Well, I must send the command to tell the CDROM device how to do after it received this command.
And by the way, as far as I tried, these three device file in /dev/ are all referred to my CDROM device, why they have so much difference?
And how can I send the SCSI command to the CDROM device through scd1 file (bloack special)?
Thanks.
Franko Fang
----- Original Message -----
From: "Greg KH" <greg@xxxxxxxxx>
To: "fangxiaozhi 00110321" <huananhu@xxxxxxxxxx>
Cc: <linux-usb@xxxxxxxxxxxxxxx>
Sent: Saturday, January 17, 2009 12:00 PM
Subject: Re: Can not send SCSI command to the cdrom device.
> 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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