On Sat, Jan 17, 2009 at 11:56:41AM +0800, fangxiaozhi 00110321 wrote:
>
> Dear all:
>
> I have a CDROM device, and after I plug it into the Linux system, the Linux system will generate three device files in the directory of /dev/, such as:
> scd1: block special (11/0)
> sr1: link to scd1
> sg1: character special(21/1)
>
> And I write a c program to send the SCSI command of SPACE to my CDROM device. Such as :
>
> fd = open("/dev/sg1", 0_RDWR);
> ioctl(fd, SCSI_IOCTL_SEND_COMMAND, cmdbuff);
>
> And I found that I can send the SPACE command to my CDROM device, if I open the file of /dev/sg1.
> But if I open the file of /dev/scd1, then I can not send the SPACE command to my CDROM device.
>
> Why I can not send SCSI command through /dev/scd1 ?
>
> What difference between /dev/sg1 and /dev/scd1 ?
One is a character device, and the other a block device.
> And how can I send send the command through /dev/scd1?
You probably can't, it is usually a different block ioctl to do that.
What are you really trying to do here?
thanks,
greg k-h
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