Date: Sun, 3 Dec 2017 12:13:16 -0500 From: Lee D <embaudarm@gmail.com> To: freebsd-hackers@freebsd.org Subject: How do I make my device driver respond to lseek? Message-ID: <CANC_bnNWfk3-QgwCEiRhMyjmQOBH%2Bt%2BXxW8zFp%2B=943nRWvJ4g@mail.gmail.com>
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Hi,
I've been trying to figure out how to make my device driver respond to
lseek(). There doesn't seem to be an appropriate entry in the cdevsw
structure (in src/sys/sys/conf.h).
Obviously I can make an ioctl() call for this (and I have, in the
interim), but I'd like to do it it the right way.
I have a feeling like I am misunderstanding some critical abstraction
layer... But at some point the device driver must be told what
position to start reading from/writing to, right?
FWIW, this is a device driver interface to a SPI flash in my custom
ARM embedded system. I need to be able to locate to a point in the
flash to read and write my app config info, without disturbing my boot
loader.
I want to be able to write code like this:
int fd = open ("/dev/my_spi_flash0", O_RDWR);
lseek(fd, 0x10000, SEEK_SET);
write(fd, buf, 100);
close(fd);
Does anyone know the proper way to implement lseek?
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