Date: Wed, 17 May 2000 16:24:40 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Joy Ganguly <joy@niksun.com> Cc: Alfred Perlstein <bright@wintelcom.net>, freebsd-hackers <freebsd-hackers@FreeBSD.ORG> Subject: Re: Question about file write???? Message-ID: <200005172324.QAA28046@apollo.backplane.com> References: <20000517160746.12768.qmail@www0a.netaddress.usa.net> <20000517102516.B14968@fw.wintelcom.net> <3922DB0F.9D9095C9@falcon.niksun.com> <20000517135644.D14968@fw.wintelcom.net> <39231E06.31DFB153@falcon.niksun.com>
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:i have a device buffer in contiguous physical memory. i want to write
:that buffer into
:a file disk. for that ive written a simple ioctl which works similar to
:the syscall
:write. except that it transfers from kernel space instead of user
:space. my user
:program calls this ioctl with the write file desc....the ioctl calls
:fp->f_ops->fo_write after setting up the uio to do the transfer.
:
:earlier the user code looked like:-
I think it would be a whole lot easier to implement mmap() on the
device, then allow the user process to mmap() the device buffer
and read() and write() it directly. I don't think you need to
implement any ioctl's for this problem.
fd = open device
ptr = mmap(...)
fd = open file
read(fd, ptr, BUFSIZE) read from file, store into device buf
...
write(fd, ptr, BUFSIZE) read from device buf, store into file
-Matt
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