Hi *,
I have one problem writing to parallel port...
From what I've tried, "outb(value, port);" works, but my problem is that
I have an app that accesses the port differently, using /dev/port
(parport0).

Now, I can't change the way the port is accessed (I'm not the author of
the app), it is huge and I do not want to rewrite it... I've managed to
recreate behavior with this simple code:

extern int errno;
int main( int argc, char **argv )
{
int fd;
char input[5];
errno = 0;

printf("Trying to open %s\n", argv[1] );

fd = open( argv[1] , O_RDWR | O_NONBLOCK );
if( fd < 0 ) {
fprintf( stderr, "Open failed with: " );
goto fail;
}
if ( strcmp(argv[2],"r")==0){
if ( read( fd, input, 5 ) < 0 ) {
fprintf( stderr, "Read failed with: " );
goto fail;
}else{
fprintf( stdout, "Read OK..\n" );
}
}else{
if ( write( fd, "hello\n", sizeof( "hello\n" ) ) < 0  ) {
fprintf( stderr, "Write failed with: " );
goto fail;
}else{
fprintf(stdout, "Write OK...");
}
}
close( fd );
exit(0);
fail:
fprintf( stderr,  strerror( errno ) );
fprintf( stderr,  "\n" );
close( fd );
exit(1);
}

for read i get in strace:

9114  fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}) 
= 0
9114  mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0xb7f30000
9114  write(1, "Trying to open /dev/parport0\n", 29) = 29
9114  open("/dev/parport0", O_RDWR|O_NONBLOCK) = 3
9114  read(3, 0xbfe4e553, 5)            = -1 EINVAL (Invalid argument)
9114  write(2, "Read failed with: ", 18) = 18
9114  write(2, "Invalid argument", 16)  = 16



and for write I get much the same thing:
9149  fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}) 
= 0
9149  mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0xb7f9c000
9149  write(1, "Trying to open /dev/parport0\n", 29) = 29
9149  open("/dev/parport0", O_RDWR|O_NONBLOCK) = 3
9149  write(3, "hello\n\0", 7)          = -1 EINVAL (Invalid argument)
9149  write(2, "Write failed with: ", 19) = 19
9149  write(2, "Invalid argument", 16)  = 16


I've tried all the commands as root.

bash# ls -l /dev/parport0
crw-rw---- 1 root lp 99, 0 2007-03-25 22:25 /dev/parport0
bash# grep ppdev /proc/devices
99 ppdev
bash# modprobe -l|grep ppdev
/lib/modules/2.6.17-11-generic/kernel/drivers/char/ppdev.ko

Port is set up as EPP in BIOS.

bash# dmesg |grep par
[17179590.040000] parport: PnPBIOS parport detected.
[17179590.040000] parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE
,EPP]
[17179591.400000] lp0: using parport0 (interrupt-driven).
[17183898.736000] ppdev: user-space parallel port driver
[17184446.412000] ppdev0: registered pardevice


Any help appreciated...

[ Post a follow-up to this message ]

On Mar 25, 10:56 pm, FrenKy <fre...@foo.com> wrote:
> Hi *,
> I have one problem writing to parallel port...
> From what I've tried, "outb(value, port);" works, but my problem is that
> I have an app that accesses the port differently, using /dev/port
> (parport0).
>
> Now, I can't change the way the port is accessed (I'm not the author of
> the app), it is huge and I do not want to rewrite it... I've managed to
> recreate behavior with this simple code:
>
> extern int errno;
> int main( int argc, char **argv )
> {
>         int fd;
>         char input[5];
>         errno = 0;
>
>         printf("Trying to open %s\n", argv[1] );
>
>         fd = open( argv[1] , O_RDWR | O_NONBLOCK );
>         if( fd < 0 ) {
>                 fprintf( stderr, "Open failed with: " );
>                 goto fail;
>         }
>         if ( strcmp(argv[2],"r")==0){
>             if ( read( fd, input, 5 ) < 0 ) {
>                 fprintf( stderr, "Read failed with: " );
>                 goto fail;
>             }else{
>                 fprintf( stdout, "Read OK..\n" );
>             }
>         }else{
>             if ( write( fd, "hello\n", sizeof( "hello\n" ) ) < 0  ) {
>                 fprintf( stderr, "Write failed with: " );
>                 goto fail;
>             }else{
>                 fprintf(stdout, "Write OK...");
>             }
>         }
>         close( fd );
>         exit(0);
> fail:
>         fprintf( stderr,  strerror( errno ) );
>         fprintf( stderr,  "\n" );
>         close( fd );
>         exit(1);
>
> }
>
> for read i get in strace:
>
> 9114  fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}
) = 0
> 9114  mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
> -1, 0) = 0xb7f30000
> 9114  write(1, "Trying to open /dev/parport0\n", 29) = 29
> 9114  open("/dev/parport0", O_RDWR|O_NONBLOCK) = 3
> 9114  read(3, 0xbfe4e553, 5)            = -1 EINVAL (Invalid argument)
> 9114  write(2, "Read failed with: ", 18) = 18
> 9114  write(2, "Invalid argument", 16)  = 16
>
> and for write I get much the same thing:
> 9149  fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}
) = 0
> 9149  mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
> -1, 0) = 0xb7f9c000
> 9149  write(1, "Trying to open /dev/parport0\n", 29) = 29
> 9149  open("/dev/parport0", O_RDWR|O_NONBLOCK) = 3
> 9149  write(3, "hello\n\0", 7)          = -1 EINVAL (Invalid argument)
> 9149  write(2, "Write failed with: ", 19) = 19
> 9149  write(2, "Invalid argument", 16)  = 16
>
> I've tried all the commands as root.
>
> bash# ls -l /dev/parport0
> crw-rw---- 1 root lp 99, 0 2007-03-25 22:25 /dev/parport0
> bash# grep ppdev /proc/devices
>  99 ppdev
> bash# modprobe -l|grep ppdev
> /lib/modules/2.6.17-11-generic/kernel/drivers/char/ppdev.ko
>
> Port is set up as EPP in BIOS.
>
> bash# dmesg |grep par
> [17179590.040000] parport: PnPBIOS parport detected.
> [17179590.040000] parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTA
TE,EPP]
> [17179591.400000] lp0: using parport0 (interrupt-driven).
> [17183898.736000] ppdev: user-space parallel port driver
> [17184446.412000] ppdev0: registered pardevice
>
> Any help appreciated...

Here's a dumb shot-in-the-dark:

> [17184446.412000] ppdev0: registered pardevice

Isn't that the device you want? I'm only guessing but:
parport0 is the physical device the kernel sees;
lp0 is the printer port the kernel would hand to say, cups;
ppdev0 is the abstracted port for user use?

HTH,
Tarkin

[ Post a follow-up to this message ]

Tarkin wrote:
> On Mar 25, 10:56 pm, FrenKy <fre...@foo.com> wrote: 
>
> Here's a dumb shot-in-the-dark:
> 
>
> Isn't that the device you want? I'm only guessing but:
> parport0 is the physical device the kernel sees;
> lp0 is the printer port the kernel would hand to say, cups;
> ppdev0 is the abstracted port for user use?
>
> HTH,
>   Tarkin
>
Hi,
Thanks for answer, but I don't understand what you mean...

Are you saying that I should have /dev/ppdev0? I do not have such device...
If I load 'lp' driver I have /dev/lp0, and if I load 'ppdev' driver I
have /dev/parport0 parallel device.
In either case, I do not have /dev/ppdev0.

Br,
FrenKy

[ Post a follow-up to this message ]

On Mar 26, 6:30 am, FrenKy <fre...@foo.com> wrote:
> Tarkin wrote: 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>
> Hi,
> Thanks for answer, but I don't understand what you mean...
>
> Are you saying that I should have /dev/ppdev0? I do not have such device..
.
> If I load 'lp' driver I have /dev/lp0, and if I load 'ppdev' driver I
> have /dev/parport0 parallel device.
> In either case, I do not have /dev/ppdev0.
>
> Br,
> FrenKy

As I said, it was a stab in the dark looking at the output
of what you had.

Some quick Googling turns up:

Some notes on writing a parport driver:
http://www.linux.com/guides/khg/Hyp...s/parport.shtml

A bunch o' documentation from RedHat on ppdev:
http://people.redhat.com/twaugh/parport/html/ppdev.html

The latter says you were on the right track, accessing through
/dev/parport0 - my guess was both ignorant &wrong   :^(

There is a mailing list here (or least directions on how to subscribe
to it):
http://www.torque.net/linux-pp.html

HTH,
Tarkin

[ Post a follow-up to this message ]