Fwd: USB - Generic Serial device : Unable to read more than 4095 bytes
Hi,
Regarding the above issue, I was checking the USB- Generic driver,
And I tried the following things and found my data loss issue is fixed.
change point
In usb_serial_probe() function in usb-serial.c
/* set up the endpoint information */
for (i = 0; i num_bulk_in; ++i) {
endpoint = bulk_in_endpoint[i];
port = serial-port[i];
buffer_size = max_t(int, serial-type-bulk_in_size,
usb_endpoint_maxp(endpoint));
buffer_size = 16384;
..
..
I changed the buffer_size value used in urb, previously it was 64
bytes now it is 16384 and I found my data loss issue fixed.
Could you tell me is there any issue with this changes ?
I am using this driver in embedded platform and in my application
other devices will not use USB -Generic driver.
Regards,
Arun
On Sat, Aug 8, 2015 at 2:50 AM, Greg KH gre...@linuxfoundation.org wrote:
On Fri, Aug 07, 2015 at 07:26:15PM +0900, arun k wrote:
Hi,
I am stuck with the above issue,
I have some doubts regarding USB - Generic driver
1. Could you please explain me why USB - Generic driver is slow ?
Because it was designed that way, it is not for high-speed data
throughput at all. It is a stop-gap measure for dumb usb devices that
want to emulate a serial connection. If you need a real driver, to
handle high rates of data, you will need to write a new driver for it.
2. Now I am try to study USB - Generic driver implementation , I am
confused with the function usb_serial_generic_read_bulk_callback() ,
could you please tell me from where this function is calling ?
I recommend reading the USB chapter in the Linux Device Drivers book
(version 3, free online) to understand how USB drivers work. After
that, the answer should be obvious (hint, look at where that function
pointer is assigned to something...)
3. If you have any detailed doc regarding the implementation of USB -
Generic serial driver, Please send to me,
The source code is pretty well documented :)
thanks,
greg k-h
--
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Re: USB - Generic Serial device : Unable to read more than 4095 bytes
Hi, I am stuck with the above issue, I have some doubts regarding USB - Generic driver 1. Could you please explain me why USB - Generic driver is slow ? 2. Now I am try to study USB - Generic driver implementation , I am confused with the function usb_serial_generic_read_bulk_callback() , could you please tell me from where this function is calling ? 3. If you have any detailed doc regarding the implementation of USB - Generic serial driver, Please send to me, Regards, Arun On Thu, Aug 6, 2015 at 3:42 PM, arun k arunkarunakara...@gmail.com wrote: / # lsusb -v Bus 002 Device 006: ID 045b:0218 Bus 001 Device 001: ID 1d6b:0002 Bus 002 Device 001: ID 1d6b:0001 Bus 003 Device 001: ID 1d6b:0002 Bus 004 Device 001: ID 1d6b:0003 In this my device is Bus 002 Device 006: ID 045b:0218 I enabled data dumping in usb_serial_generic_read_bulk_callback() function and found data received in this function is losing. In this function data is received as 64 bytes packets and two continuous 64 bytes having no data loss but the next packets are lost ie 1st packet ok(64 byte) 2nd packet ok(64 byte) . . packet lossing . 7th packet ok(64 byte) 8th packet ok(64 byte) . . In this way data loss is happening. Number of packets losing is different not constant always. I think the generic USB driver ignores baud rate. Like Greg suggested, you need to use the proper driver for your hardware. I did't find any other suitable driver inside Linux. I checked this device in windows in that usbser.sys is detecting(.inf file is attached with the mail). Could you suggest any available drivers for my device. Sorry I am very new to Linux drivers. I will post my USB device descriptor values below [ 1291.908071] ## udev-descriptor.bLength 0x12 [ 1291.908089] ## udev-descriptor.bDescriptorType 0x1 [ 1291.908147] ## udev-descriptor.bcdUSB 0x200 [ 1291.908165] ## udev-descriptor.bDeviceClass 0xef [ 1291.908181] ## udev-descriptor.bDeviceSubClass 0x2 [ 1291.908196] ## udev-descriptor.bDeviceProtocol 0x1 [ 1291.908211] ## udev-descriptor.bMaxPacketSize0 0x40 [ 1291.908226] ## udev-descriptor.idVendor 0x45b [ 1291.908241] ## udev-descriptor.idProduct 0x218 [ 1291.908255] ## udev-descriptor.bcdDevice 0x1 [ 1291.908270] ## udev-descriptor.iManufacturer 0x0 [ 1291.908284] ## udev-descriptor.iProduct 0x0 [ 1291.908298] ## udev-descriptor.iSerialNumber 0x0 [ 1291.908313] ## udev-descriptor.bNumConfigurations 0x1 Regards, Arun On Wed, Aug 5, 2015 at 9:31 PM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/04/2015 11:57 PM, arun k wrote: Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? I am not sure about this. I need to check this. Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem I tried B115200 also but issue is still there. I think the generic USB driver ignores baud rate. Like Greg suggested, you need to use the proper driver for your hardware. What is the output from 'lsusb -v' and please identify in that output which device you are using. I am using a USB device and that sending data at a rate of *409600 bytes/sec*. Is this data rate have any relation with issue. Yes. Also, can you test this on a newer kernel like 3.18? Regards, Peter Hurley On Wed, Aug 5, 2015 at 11:24 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/04/2015 10:00 PM, arun k wrote: I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem. Regards, Peter Hurley On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On 08/06/2015 02:42 AM, arun k wrote: / # lsusb -v Bus 002 Device 006: ID 045b:0218 Bus 001 Device 001: ID 1d6b:0002 Bus 002 Device 001: ID 1d6b:0001 Bus 003 Device 001: ID 1d6b:0002 Bus 004 Device 001: ID 1d6b:0003 In this my device is Bus 002 Device 006: ID 045b:0218 I have no idea what this device is, sorry. And the device descriptor dump below is not very helpful because it doesn't have the configurations. What is this for? I enabled data dumping in usb_serial_generic_read_bulk_callback() function and found data received in this function is losing. In this function data is received as 64 bytes packets and two continuous 64 bytes having no data loss but the next packets are lost ie 1st packet ok(64 byte) 2nd packet ok(64 byte) . . packet lossing . 7th packet ok(64 byte) 8th packet ok(64 byte) . . In this way data loss is happening. Number of packets losing is different not constant always. It's unclear what you are saying here; are you saying (a) the sending device is dropping data so the urbs do not contain the data you expect, or (b) all of the data is being received but the not all of it is being buffered. Either way, the fundamental problem you have is that your reader is not fast enough. What is your application? Have you tried a simple test jig that only reads data without processing it to see if the application is the problem? What h/w platform is this? You mentioned earlier you're running 3.4.35. That's really old; current 3.4 is .108. Where did you get this kernel? Regards, Peter Hurley PS - Please stop top-posting. See how I had to reiterate your linux version... I think the generic USB driver ignores baud rate. Like Greg suggested, you need to use the proper driver for your hardware. I did't find any other suitable driver inside Linux. I checked this device in windows in that usbser.sys is detecting(.inf file is attached with the mail). Could you suggest any available drivers for my device. Sorry I am very new to Linux drivers. I will post my USB device descriptor values below [ 1291.908071] ## udev-descriptor.bLength 0x12 [ 1291.908089] ## udev-descriptor.bDescriptorType 0x1 [ 1291.908147] ## udev-descriptor.bcdUSB 0x200 [ 1291.908165] ## udev-descriptor.bDeviceClass 0xef [ 1291.908181] ## udev-descriptor.bDeviceSubClass 0x2 [ 1291.908196] ## udev-descriptor.bDeviceProtocol 0x1 [ 1291.908211] ## udev-descriptor.bMaxPacketSize0 0x40 [ 1291.908226] ## udev-descriptor.idVendor 0x45b [ 1291.908241] ## udev-descriptor.idProduct 0x218 [ 1291.908255] ## udev-descriptor.bcdDevice 0x1 [ 1291.908270] ## udev-descriptor.iManufacturer 0x0 [ 1291.908284] ## udev-descriptor.iProduct 0x0 [ 1291.908298] ## udev-descriptor.iSerialNumber 0x0 [ 1291.908313] ## udev-descriptor.bNumConfigurations 0x1 Regards, Arun On Wed, Aug 5, 2015 at 9:31 PM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/04/2015 11:57 PM, arun k wrote: Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? I am not sure about this. I need to check this. Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem I tried B115200 also but issue is still there. I think the generic USB driver ignores baud rate. Like Greg suggested, you need to use the proper driver for your hardware. What is the output from 'lsusb -v' and please identify in that output which device you are using. I am using a USB device and that sending data at a rate of *409600 bytes/sec*. Is this data rate have any relation with issue. Yes. Also, can you test this on a newer kernel like 3.18? Regards, Peter Hurley On Wed, Aug 5, 2015 at 11:24 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/04/2015 10:00 PM, arun k wrote: I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem. Regards, Peter Hurley On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On Fri, Aug 07, 2015 at 07:26:15PM +0900, arun k wrote: Hi, I am stuck with the above issue, I have some doubts regarding USB - Generic driver 1. Could you please explain me why USB - Generic driver is slow ? Because it was designed that way, it is not for high-speed data throughput at all. It is a stop-gap measure for dumb usb devices that want to emulate a serial connection. If you need a real driver, to handle high rates of data, you will need to write a new driver for it. 2. Now I am try to study USB - Generic driver implementation , I am confused with the function usb_serial_generic_read_bulk_callback() , could you please tell me from where this function is calling ? I recommend reading the USB chapter in the Linux Device Drivers book (version 3, free online) to understand how USB drivers work. After that, the answer should be obvious (hint, look at where that function pointer is assigned to something...) 3. If you have any detailed doc regarding the implementation of USB - Generic serial driver, Please send to me, The source code is pretty well documented :) thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On 08/04/2015 11:57 PM, arun k wrote: Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? I am not sure about this. I need to check this. Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem I tried B115200 also but issue is still there. I think the generic USB driver ignores baud rate. Like Greg suggested, you need to use the proper driver for your hardware. What is the output from 'lsusb -v' and please identify in that output which device you are using. I am using a USB device and that sending data at a rate of *409600 bytes/sec*. Is this data rate have any relation with issue. Yes. Also, can you test this on a newer kernel like 3.18? Regards, Peter Hurley On Wed, Aug 5, 2015 at 11:24 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/04/2015 10:00 PM, arun k wrote: I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem. Regards, Peter Hurley On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com mailto:pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Fwd: USB - Generic Serial device : Unable to read more than 4095 bytes
-- Forwarded message -- From: arun k arunkarunakara...@gmail.com Date: Wed, Aug 5, 2015 at 12:57 PM Subject: Re: USB - Generic Serial device : Unable to read more than 4095 bytes To: Peter Hurley pe...@hurleysoftware.com Cc: Greg KH gre...@linuxfoundation.org, linux-usb@vger.kernel.org Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? I am not sure about this. I need to check this. Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem I tried B115200 also but issue is still there. I am using a USB device and that sending data at a rate of 409600 bytes/sec. Is this data rate have any relation with issue. Regards, Arun On Wed, Aug 5, 2015 at 11:24 AM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/04/2015 10:00 PM, arun k wrote: I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem. Regards, Peter Hurley On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); But I still having the data loss issue. Regards Arun On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On 08/04/2015 10:00 PM, arun k wrote: I enabled software flow control like below tty.c_iflag |= (IXON | IXOFF | IXANY); Ok, but does the sending device know how to process in-band software flow control and is it set up to respond properly? Also, I doubt software flow control is going to work @ 4Mbaud line rate. If you're stuck using software flow control, start with a 115kbaud line rate and see if that fixes your data loss problem. Regards, Peter Hurley On Wed, Aug 5, 2015 at 12:59 AM, Peter Hurley pe...@hurleysoftware.com wrote: On 08/03/2015 10:47 PM, arun k wrote: Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? The data loss is probably occurring because you have all flow control disabled and the line speed is too fast for no flow control. Regards, Peter Hurley Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org mailto:gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Fwd: USB - Generic Serial device : Unable to read more than 4095 bytes
Thank you for the reply The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. I tried this method but in my case I found data loss. By changing any buffer size modification in driver side , can we fix this issue ? Please don't use the generic driver, it's slow and not the best to use Could you tell me is generic driver is suitable for my application ( My usb device sending data at a rate of 409600 bytes/sec) , ? or do you have any other suggestion for me ? My Linux kernel version is 3.4.35 Regards, Arun On Tue, Aug 4, 2015 at 1:13 AM, Greg KH gre...@linuxfoundation.org wrote: On Mon, Aug 03, 2015 at 04:44:07PM +0900, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. Please don't use the generic driver, it's slow and not the best to use. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 The tty layer is limiting you, just keep reading in a loop until you run out of data, you should not ever expect to read a specific number of bytes from a tty device at a time, the read call will tell you the number that was read properly. thanks, greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
USB - Generic Serial device : Unable to read more than 4095 bytes
Hi ,
I have a trouble with using usb serial generic device.
I am using USB - Generic Serial driver for communicating with my usb
device and my embedded device.
My usb device sending data at a rate of 409600 bytes/sec, and in host
side application I tried to read 16384 bytes in one read. But the read
size returning is always 4095
I don't know whether I missed any settings or this is limited in driver.
Could you please tell me is it possible to read large size(16384
bytes) using usb serial generic driver.
I pasted my sample code for reading from usb device
###
/*
* usb_logger_test.c
*
* Created on: Aug 3, 2015
* Author:
*/
#include stdio.h
#include stdlib.h
#include string.h
#include sys/types.h
#include sys/stat.h
#include fcntl.h
#include termios.h
#include unistd.h
#include errno.h
#include poll.h
#define USB_DEVICE /dev/ttyUSB0
#define DATA_SIZE (16384)
//#define DATA_SIZE (1000)
struct pollfd fds[1];
nfds_t nfds = 1;
int dev_fd;
void set_blocking (int should_block)
{
struct termios tty;
memset (tty, 0, sizeof tty);
if (tcgetattr (dev_fd, tty) != 0) {
printf(error %d from tggetattr, errno);
return;
}
tty.c_cc[VMIN] = should_block ? 1 : 0;
//tty.c_cc[VTIME] = 5;// 0.5 seconds read timeout
if (tcsetattr (dev_fd, TCSANOW, tty) != 0) {
printf(error %d setting term attributes, errno);
}
}
int hal_uart_init()
{
int parity =0;
int speed = B115200;
struct termios tty;
memset ((void *)tty, 0, sizeof tty);
if (tcgetattr (dev_fd, tty) != 0) {
printf(error %d from tcgetattr, errno);
return -1;
}
cfsetospeed (tty, speed);
cfsetispeed (tty, speed);
tty.c_cflag = (tty.c_cflag ~CSIZE) | CS8; // 8-bit chars
// disable IGNBRK for mismatched speed tests; otherwise receive break
// as \000 chars
tty.c_iflag = ~IGNBRK; // disable break processing
tty.c_lflag = 0;// no signaling chars, no echo,
// no canonical processing
tty.c_oflag = 0;// no remapping, no delays
tty.c_cc[VMIN] = 0;// read doesn't block
tty.c_cc[VTIME] = 5;// 0.5 seconds read timeout
tty.c_iflag = ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
// enable reading
tty.c_cflag = ~(PARENB | PARODD); // shut off parity
tty.c_cflag |= parity;
tty.c_cflag = ~CSTOPB;
tty.c_cflag = ~CRTSCTS;
tty.c_iflag = ~(ICRNL | IGNCR );
if (tcsetattr (dev_fd, TCSANOW, tty) != 0) {
printf(error %d from tcsetattr, errno);
return -1;
}
set_blocking (1);
return 0;
}
int hal_uart_open()
{
dev_fd = open (USB_DEVICE,O_RDWR | O_NOCTTY | O_SYNC);
if (dev_fd 0) {
printf (error %d opening %s: %s, errno, USB_DEVICE, strerror (errno));
return -1;
}
fds[0].fd = dev_fd; /* open fd for each filter,increment nfds */
fds[0].events = POLLIN;
fds[0].revents = 0;
nfds = 1;
return 0;
}
int hal_uart_read(unsigned char *buf, unsigned int size, unsigned int *rcv_len)
{
int ret;
unsigned int timeout = 1000;
int read_size;
ret = poll(fds[0], nfds, timeout);
if(ret = 0) {
if(ret 0) {
printf( poll err !!! errno %d : %s !!! \n, errno, strerror(errno));
return -1;
}else {
printf( poll timeout !!! , timeout %d \n, timeout);
return -1;
}
}
if(fds[0].revents POLLIN) {
read_size = read(fds[0].fd, buf, DATA_SIZE);
if(read_size = 0) {
printf( read err !!! read_size %d fd %d errno %d : %s !!! \n,
read_size, fds[0].fd, timeout, errno, strerror(errno));
return -1;
}
printf(read succc read_size %d \n, read_size);
{
FILE *fp = fopen(usb_dump, ab );
if(fp != NULL) {
fwrite(buf, 1, read_size, fp);
fflush(fp);
fclose(fp);
}
}
}else {
printf( No data read \n);
}
return read_size;
}
void main()
{
unsigned char buf[DATA_SIZE];
unsigned int size;
unsigned int rcv_len;
int ret = 0;
ret = hal_uart_open();
if(ret 0) {
printf(hal_uart_open fail \n);
return;
}
ret = hal_uart_init();
if(ret 0) {
printf(hal_uart_init fail \n);
return;
}
while(1) {
hal_uart_read(buf[0], size, rcv_len);
//usleep(40);
usleep(4);
//sleep(10);
//sleep(11);
}
}
Regards,
Arun
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Re: USB - Generic Serial device : Unable to read more than 4095 bytes
On 08/03/2015 03:44 AM, arun k wrote: Hi , I have a trouble with using usb serial generic device. I am using USB - Generic Serial driver for communicating with my usb device and my embedded device. My usb device sending data at a rate of 409600 bytes/sec, and in host side application I tried to read 16384 bytes in one read. But the read size returning is always 4095 I don't know whether I missed any settings or this is limited in driver. Could you please tell me is it possible to read large size(16384 bytes) using usb serial generic driver. read() is limited to 4096 bytes by the driver. What linux version are you using? Regards, Peter Hurley -- To unsubscribe from this list: send the line unsubscribe linux-usb in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
