RE: mmap() and ioctl()
>-Original Message- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Matthew Dharm >Sent: Monday, April 04, 2005 12:20 PM >To: Richard B. Johnson >Cc: Kernel Developer List >Subject: Re: mmap() and ioctl() > [snip] >That's an interesting concept, and one I'm not familiar with. >Any useful >pointers (beyond UTSL)? I'll admit to being much more >familiar with SCSI >and USB internals than I am with something like device-layer >interfacing. Try this: http://lwn.net/Kernel/LDD3/ Aleks. - 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: mmap() and ioctl()
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Matthew Dharm Sent: Monday, April 04, 2005 12:20 PM To: Richard B. Johnson Cc: Kernel Developer List Subject: Re: mmap() and ioctl() [snip] That's an interesting concept, and one I'm not familiar with. Any useful pointers (beyond UTSL)? I'll admit to being much more familiar with SCSI and USB internals than I am with something like device-layer interfacing. Try this: http://lwn.net/Kernel/LDD3/ Aleks. - 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: mmap() and ioctl()
On Mon, Apr 04, 2005 at 03:02:26PM -0400, Richard B. Johnson wrote: > On Mon, 4 Apr 2005, Matthew Dharm wrote: > > >This probably is a silly question, but > > > >Is is possible to open a file, mmap() it into memory, then pass the address > >of that map via an ioctl() call to the kernel, which will copy_from_user() > >that data? > > > > Yes. A user-mode pointer, passed via ioctl() is valid in the kernel > in the context of the user, i.e., during read() write() ioctl(). > > However, it is not valid if it is accessed by some other process or > an interrupt. In other words, you can't store it somewhere and > access it later in some other context. Right, I've got that part. The plan has been to mmap(), ioctl(), and inside the ioctl do a copy_from_user() into a kernel-context buffer. > >Yeah, that's an odd concept, I know... I could always malloc() some > >memory, read the file in, and then ioctl() it. But, if I could get away > >with a direct mmap(), that would be much better for me. > > Since you need to copy anyway, you could mmap() your kernel > data (impliment mmap in your driver). Then you mmap both > "files" the same way and copy to/from in user-mode. That's an interesting concept, and one I'm not familiar with. Any useful pointers (beyond UTSL)? I'll admit to being much more familiar with SCSI and USB internals than I am with something like device-layer interfacing. It sounds like you're saying that my driver can implement an mmap() method (similar to the ioctl method), and then I can just mmap the source file and the driver /dev node and do a memcpy() between them. That's an interesting idea, but potentially not what I need. The data needs to go with some command information and a buffer to stuff the results in. This is basically a co-processor device I'm talking to. The basic data path here is from a file, through the driver, to a custom piece of hardware (and back again). Tho, anything that allows me to move the data from the disk up to a place where I can pci_map_single() it faster is a Good Thing(tm). Matt -- Matthew Dharm Home: [EMAIL PROTECTED] Maintainer, Linux USB Mass Storage Driver Sir, for the hundreth time, we do NOT carry 600-round boxes of belt-fed suction darts! -- Salesperson to Greg User Friendly, 12/30/1997 pgplo8XgKAdOM.pgp Description: PGP signature
Re: mmap() and ioctl()
On Mon, 4 Apr 2005, Matthew Dharm wrote: This probably is a silly question, but Is is possible to open a file, mmap() it into memory, then pass the address of that map via an ioctl() call to the kernel, which will copy_from_user() that data? Yes. A user-mode pointer, passed via ioctl() is valid in the kernel in the context of the user, i.e., during read() write() ioctl(). However, it is not valid if it is accessed by some other process or an interrupt. In other words, you can't store it somewhere and access it later in some other context. Yeah, that's an odd concept, I know... I could always malloc() some memory, read the file in, and then ioctl() it. But, if I could get away with a direct mmap(), that would be much better for me. Matt Since you need to copy anyway, you could mmap() your kernel data (impliment mmap in your driver). Then you mmap both "files" the same way and copy to/from in user-mode. Cheers, Dick Johnson Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips). Notice : All mail here is now cached for review by Dictator Bush. 98.36% of all statistics are fiction. - 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/
mmap() and ioctl()
This probably is a silly question, but Is is possible to open a file, mmap() it into memory, then pass the address of that map via an ioctl() call to the kernel, which will copy_from_user() that data? Yeah, that's an odd concept, I know... I could always malloc() some memory, read the file in, and then ioctl() it. But, if I could get away with a direct mmap(), that would be much better for me. Matt -- Matthew Dharm Home: [EMAIL PROTECTED] Maintainer, Linux USB Mass Storage Driver I say, what are all those naked people doing? -- Big client to Stef User Friendly, 12/14/1997 pgpvU4zFwKbOy.pgp Description: PGP signature
mmap() and ioctl()
This probably is a silly question, but Is is possible to open a file, mmap() it into memory, then pass the address of that map via an ioctl() call to the kernel, which will copy_from_user() that data? Yeah, that's an odd concept, I know... I could always malloc() some memory, read the file in, and then ioctl() it. But, if I could get away with a direct mmap(), that would be much better for me. Matt -- Matthew Dharm Home: [EMAIL PROTECTED] Maintainer, Linux USB Mass Storage Driver I say, what are all those naked people doing? -- Big client to Stef User Friendly, 12/14/1997 pgpvU4zFwKbOy.pgp Description: PGP signature
Re: mmap() and ioctl()
On Mon, 4 Apr 2005, Matthew Dharm wrote: This probably is a silly question, but Is is possible to open a file, mmap() it into memory, then pass the address of that map via an ioctl() call to the kernel, which will copy_from_user() that data? Yes. A user-mode pointer, passed via ioctl() is valid in the kernel in the context of the user, i.e., during read() write() ioctl(). However, it is not valid if it is accessed by some other process or an interrupt. In other words, you can't store it somewhere and access it later in some other context. Yeah, that's an odd concept, I know... I could always malloc() some memory, read the file in, and then ioctl() it. But, if I could get away with a direct mmap(), that would be much better for me. Matt Since you need to copy anyway, you could mmap() your kernel data (impliment mmap in your driver). Then you mmap both files the same way and copy to/from in user-mode. Cheers, Dick Johnson Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips). Notice : All mail here is now cached for review by Dictator Bush. 98.36% of all statistics are fiction. - 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: mmap() and ioctl()
On Mon, Apr 04, 2005 at 03:02:26PM -0400, Richard B. Johnson wrote: On Mon, 4 Apr 2005, Matthew Dharm wrote: This probably is a silly question, but Is is possible to open a file, mmap() it into memory, then pass the address of that map via an ioctl() call to the kernel, which will copy_from_user() that data? Yes. A user-mode pointer, passed via ioctl() is valid in the kernel in the context of the user, i.e., during read() write() ioctl(). However, it is not valid if it is accessed by some other process or an interrupt. In other words, you can't store it somewhere and access it later in some other context. Right, I've got that part. The plan has been to mmap(), ioctl(), and inside the ioctl do a copy_from_user() into a kernel-context buffer. Yeah, that's an odd concept, I know... I could always malloc() some memory, read the file in, and then ioctl() it. But, if I could get away with a direct mmap(), that would be much better for me. Since you need to copy anyway, you could mmap() your kernel data (impliment mmap in your driver). Then you mmap both files the same way and copy to/from in user-mode. That's an interesting concept, and one I'm not familiar with. Any useful pointers (beyond UTSL)? I'll admit to being much more familiar with SCSI and USB internals than I am with something like device-layer interfacing. It sounds like you're saying that my driver can implement an mmap() method (similar to the ioctl method), and then I can just mmap the source file and the driver /dev node and do a memcpy() between them. That's an interesting idea, but potentially not what I need. The data needs to go with some command information and a buffer to stuff the results in. This is basically a co-processor device I'm talking to. The basic data path here is from a file, through the driver, to a custom piece of hardware (and back again). Tho, anything that allows me to move the data from the disk up to a place where I can pci_map_single() it faster is a Good Thing(tm). Matt -- Matthew Dharm Home: [EMAIL PROTECTED] Maintainer, Linux USB Mass Storage Driver Sir, for the hundreth time, we do NOT carry 600-round boxes of belt-fed suction darts! -- Salesperson to Greg User Friendly, 12/30/1997 pgplo8XgKAdOM.pgp Description: PGP signature
