Re: porting IDE patches to PATA driver

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Alan Cox wrote:

>> controller switches to a specific DVD-LOADER mode as soon as kernel
>> sends any command to the slave device, so they had to patch sources
>> and add a strange looking command
>>
>> OUT_BYTE((head|drive->select.all) & ~(1<<4), IDE_SELECT_REG);
>>
>> everywhere the slave device is accessed to cheat the controller and
>> let it believe it talks to the master. Slave device remains active
>> because it was already selected but the controller assumes we are
>> talking to the master and does not switch to DVD-LOADER mode.
>>     
>
> That can be done in a libata driver by providing your own exec_command
> functions but again could wait. Try something like
>
> static void my_sff_exec_command(struct ata_port *ap, const struct
> 	ata_taskfile *tf)
> {
> 	iowrite8(tf->command, ap->ioaddr.command_addr);
> 	if (tf->flags & ATA_TFLAG_DEVICE)
> 		iowrite8(tf->device & ~ATA_DEV1, ap->ioaddr.device_addr);
>   

  Note that this possibly violates ATA specs that forbid writing to any 
register with BSY set -- which might well be after wroiting a command, 
despite 400 ns couldn't have passed yet. IOW, I don't advice such 
trickery -- your write may well  be ignored.

> 	ata_sff_pause(ap);
> }

MBR, Sergei