Re: How can I create or read/write a file in linux device driver?
linux-os (Dick Johnson) wrote: Sometimes a idiot boss will say; "You need to read or write files from within the driver. If you don't do what I tell you, you are fired!" To which the response is something like "This is impossible/illegal/unsupported so it can't be done." Fortunately, civilized countries have laws against being fired for being unable to do the impossible. Well, nothing is really impossible. Tell the boss about the man-hours needed to implement a kernel file API from scratch, and then forking the kernel in order to maintain this community-rejected abomination forever. Sigh, assuming you can't walk next door and get a reasonable job, it __is__ possible to unreliably access files within the kernel. Note that the kernel is __designed__ to perform user-mode operations, so it is a bit difficult. Another way is to cheat. The boss asks the impossible, so make a workaround in the form of a userspace program that does the file writing while communicationg with the driver. The driver installer software can then be made to install this userspace program as well. Looks like a hack - but it is the recommended way of doing these things. Often enough you have a startup script for the thing anyway, a good place to launch userspace helper apps. Either that, or userspace will be involved somehow in using the device - launch the helper at that time. Try not to get in a situation where the boss explicitly asks for files written from the kernel. If you're making a driver and the boss ask for a file - just write that userspace helper because that is the way it is done on linux. No conflict there. Helge Hafting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
linux-os (Dick Johnson) wrote: Sometimes a idiot boss will say; You need to read or write files from within the driver. If you don't do what I tell you, you are fired! To which the response is something like This is impossible/illegal/unsupported so it can't be done. Fortunately, civilized countries have laws against being fired for being unable to do the impossible. Well, nothing is really impossible. Tell the boss about the man-hours needed to implement a kernel file API from scratch, and then forking the kernel in order to maintain this community-rejected abomination forever. Sigh, assuming you can't walk next door and get a reasonable job, it __is__ possible to unreliably access files within the kernel. Note that the kernel is __designed__ to perform user-mode operations, so it is a bit difficult. Another way is to cheat. The boss asks the impossible, so make a workaround in the form of a userspace program that does the file writing while communicationg with the driver. The driver installer software can then be made to install this userspace program as well. Looks like a hack - but it is the recommended way of doing these things. Often enough you have a startup script for the thing anyway, a good place to launch userspace helper apps. Either that, or userspace will be involved somehow in using the device - launch the helper at that time. Try not to get in a situation where the boss explicitly asks for files written from the kernel. If you're making a driver and the boss ask for a file - just write that userspace helper because that is the way it is done on linux. No conflict there. Helge Hafting - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 09:27, linux-os (Dick Johnson) wrote: > >First, since file-operations require process context, and the kernel >is not a process, you need to create a kernel thread to handle your file >I/O. Not always. If you do file I/O as part of a device driver, you are fine. quad_dsp is such an example, where writing to /dev/Qdsp_* will trigger writes to /dev/dsp and /dev/adsp. >Once you set up this "internal environment," you use the appropriate >kernel function(s) such as sys_open() What against filp_open? That avoids the unnecessary getname() stuff in most syscalls. -`J' -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, Jan 12, 2007 at 09:27:01AM -0500, linux-os (Dick Johnson) wrote: > Sometimes a idiot boss will say; "You need to read or write files from > within the driver. If you don't do what I tell you, you are fired!" Sometimes PHBs want you to break the laws of physics. I suggest you read Dilbert about that. Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, 12 Jan 2007, Erik Mouw wrote: > On Fri, Jan 12, 2007 at 11:27:01AM +0100, Jesper Juhl wrote: >> On 12/01/07, congwen <[EMAIL PROTECTED]> wrote: >>> Hello everyone, I want to create and read/write a file in Linux kernel or >>> device driver, >> >> Don't read/write user space files from kernel space. >> >> Please search the archives, this get asked a lot and it has been >> explained a million times why it's a bad idea. >> You can also read http://www.linuxjournal.com/article/8110 > > Rather point to > > http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad > > > Erik > > -- > +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- > | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands > - Sometimes a idiot boss will say; "You need to read or write files from within the driver. If you don't do what I tell you, you are fired!" Sigh, assuming you can't walk next door and get a reasonable job, it __is__ possible to unreliably access files within the kernel. Note that the kernel is __designed__ to perform user-mode operations, so it is a bit difficult. First, since file-operations require process context, and the kernel is not a process, you need to create a kernel thread to handle your file I/O. You write code to properly start up and shut down the kernel thread before you do anything else. There are drivers in the kernel tree that can be used as templates. The code that the kernel thread executes, needs to be written so that it can receive commands to open/close/read/write files, perhaps from semaphores or other communications methods. You can't just create the thread and let it spin. It will eat up most all the CPU time! Once you set up this "internal environment," you use the appropriate kernel function(s) such as sys_open(), etc. You need to look at the code and figure out what the parameters are. This is all very scary stuff and it will take a long time to get it right. Once you have that working, there is no guarantee that it will work with another kernel version simply by recompiling it. This is because some kernel versions lock portions of kernel code that you need. It's a pain. In the unlikely event that you get a reasonably bug-free system running, please publish the code on some web-site so it can be referenced in the future by people whose bosses are idiots. Cheers, Dick Johnson Penguin : Linux version 2.6.16.24 on an i686 machine (5592.72 BogoMips). New book: http://www.AbominableFirebug.com/ _ The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [EMAIL PROTECTED] - and destroy all copies of this information, including any attachments, without reading or disclosing them. Thank you. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, Jan 12, 2007 at 11:27:01AM +0100, Jesper Juhl wrote: > On 12/01/07, congwen <[EMAIL PROTECTED]> wrote: > >Hello everyone, I want to create and read/write a file in Linux kernel or > >device driver, > > Don't read/write user space files from kernel space. > > Please search the archives, this get asked a lot and it has been > explained a million times why it's a bad idea. > You can also read http://www.linuxjournal.com/article/8110 Rather point to http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 11:54, Jesper Juhl wrote: >> >> The article does it the bad way. IMHO filp_open() and >> vfs_read/vfs_write() are much less problematic wrt. to userspace. >> FWIW see >> ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 > > There is no good way. You simply should NOT do it. I never said there is a good way, just that some are better than others ;-) As for quad_dsp, well, the reason why it's done in kernel-space is because userspace wrapping with LD_PRELOAD does not always work, esp. with statically compiled apps. -`J' -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On 12/01/07, Jan Engelhardt <[EMAIL PROTECTED]> wrote: On Jan 12 2007 11:27, Jesper Juhl wrote: > On 12/01/07, congwen <[EMAIL PROTECTED]> wrote: >> Hello everyone, I want to create and read/write a file in Linux kernel or >> device driver, > > Don't read/write user space files from kernel space. > > Please search the archives, this get asked a lot and it has been > explained a million times why it's a bad idea. > You can also read http://www.linuxjournal.com/article/8110 The article does it the bad way. IMHO filp_open() and vfs_read/vfs_write() are much less problematic wrt. to userspace. FWIW see ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 There is no good way. You simply should NOT do it. -- Jesper Juhl <[EMAIL PROTECTED]> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 11:27, Jesper Juhl wrote: > On 12/01/07, congwen <[EMAIL PROTECTED]> wrote: >> Hello everyone, I want to create and read/write a file in Linux kernel or >> device driver, > > Don't read/write user space files from kernel space. > > Please search the archives, this get asked a lot and it has been > explained a million times why it's a bad idea. > You can also read http://www.linuxjournal.com/article/8110 The article does it the bad way. IMHO filp_open() and vfs_read/vfs_write() are much less problematic wrt. to userspace. FWIW see ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 -`J' -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On 12/01/07, congwen <[EMAIL PROTECTED]> wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 -- Jesper Juhl <[EMAIL PROTECTED]> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On 12/01/07, congwen [EMAIL PROTECTED] wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 -- Jesper Juhl [EMAIL PROTECTED] Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 11:27, Jesper Juhl wrote: On 12/01/07, congwen [EMAIL PROTECTED] wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 The article does it the bad way. IMHO filp_open() and vfs_read/vfs_write() are much less problematic wrt. to userspace. FWIW see ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 -`J' -- - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On 12/01/07, Jan Engelhardt [EMAIL PROTECTED] wrote: On Jan 12 2007 11:27, Jesper Juhl wrote: On 12/01/07, congwen [EMAIL PROTECTED] wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 The article does it the bad way. IMHO filp_open() and vfs_read/vfs_write() are much less problematic wrt. to userspace. FWIW see ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 There is no good way. You simply should NOT do it. -- Jesper Juhl [EMAIL PROTECTED] Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 11:54, Jesper Juhl wrote: The article does it the bad way. IMHO filp_open() and vfs_read/vfs_write() are much less problematic wrt. to userspace. FWIW see ftp://ftp-1.gwdg.de/pub/linux/misc/suser-jengelh/kernel/quad_dsp-1.5.1.tar.bz2 There is no good way. You simply should NOT do it. I never said there is a good way, just that some are better than others ;-) As for quad_dsp, well, the reason why it's done in kernel-space is because userspace wrapping with LD_PRELOAD does not always work, esp. with statically compiled apps. -`J' -- - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, Jan 12, 2007 at 11:27:01AM +0100, Jesper Juhl wrote: On 12/01/07, congwen [EMAIL PROTECTED] wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 Rather point to http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, 12 Jan 2007, Erik Mouw wrote: On Fri, Jan 12, 2007 at 11:27:01AM +0100, Jesper Juhl wrote: On 12/01/07, congwen [EMAIL PROTECTED] wrote: Hello everyone, I want to create and read/write a file in Linux kernel or device driver, Don't read/write user space files from kernel space. Please search the archives, this get asked a lot and it has been explained a million times why it's a bad idea. You can also read http://www.linuxjournal.com/article/8110 Rather point to http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - Sometimes a idiot boss will say; You need to read or write files from within the driver. If you don't do what I tell you, you are fired! Sigh, assuming you can't walk next door and get a reasonable job, it __is__ possible to unreliably access files within the kernel. Note that the kernel is __designed__ to perform user-mode operations, so it is a bit difficult. First, since file-operations require process context, and the kernel is not a process, you need to create a kernel thread to handle your file I/O. You write code to properly start up and shut down the kernel thread before you do anything else. There are drivers in the kernel tree that can be used as templates. The code that the kernel thread executes, needs to be written so that it can receive commands to open/close/read/write files, perhaps from semaphores or other communications methods. You can't just create the thread and let it spin. It will eat up most all the CPU time! Once you set up this internal environment, you use the appropriate kernel function(s) such as sys_open(), etc. You need to look at the code and figure out what the parameters are. This is all very scary stuff and it will take a long time to get it right. Once you have that working, there is no guarantee that it will work with another kernel version simply by recompiling it. This is because some kernel versions lock portions of kernel code that you need. It's a pain. In the unlikely event that you get a reasonably bug-free system running, please publish the code on some web-site so it can be referenced in the future by people whose bosses are idiots. Cheers, Dick Johnson Penguin : Linux version 2.6.16.24 on an i686 machine (5592.72 BogoMips). New book: http://www.AbominableFirebug.com/ _ The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [EMAIL PROTECTED] - and destroy all copies of this information, including any attachments, without reading or disclosing them. Thank you. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Fri, Jan 12, 2007 at 09:27:01AM -0500, linux-os (Dick Johnson) wrote: Sometimes a idiot boss will say; You need to read or write files from within the driver. If you don't do what I tell you, you are fired! Sometimes PHBs want you to break the laws of physics. I suggest you read Dilbert about that. Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: How can I create or read/write a file in linux device driver?
On Jan 12 2007 09:27, linux-os (Dick Johnson) wrote: First, since file-operations require process context, and the kernel is not a process, you need to create a kernel thread to handle your file I/O. Not always. If you do file I/O as part of a device driver, you are fine. quad_dsp is such an example, where writing to /dev/Qdsp_* will trigger writes to /dev/dsp and /dev/adsp. Once you set up this internal environment, you use the appropriate kernel function(s) such as sys_open() What against filp_open? That avoids the unnecessary getname() stuff in most syscalls. -`J' -- - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
