Re: [PATCH] SH/Dreamcast - add support for GD-Rom CDROM drive on

Andrew Morton
2008-01-12T19:15:20Z

On Sat, 12 Jan 2008 14:14:01 +0000 Adrian McMenamin <adrian@newgolddream.dyndns.info> wrote:

>
> > > + spin_command->cmd[0] = 0x70;
> > > + spin_command->cmd[2] = 0x1f;
> > > + spin_command->buflen = 0;
> > > + gd.pending = 1;
> > > + gdrom_packetcommand(gd.cd_info, spin_command);
> > > + /* 60 second timeout */
> > > + wait_event_interruptible_timeout(command_queue, gd.pending = 0, HZ * 60);
> > > + gd.pending = 0;
> > > + kfree(spin_command);
> > > + if (gd.status & 0x01) {
> > > + /* log an error */
> > > + gdrom_getsense(NULL);
> > > + return -EIO;
> > > + }
> > > + return 0;
> > > +}
> >
> > If the wait_event_interruptible_timeout() indeed times out, we go ahead and
> > free spin_command. But someone else could potentially be using it.
> >
> > Suppose gdrom_packetcommand() got stuck for a minute due to bad hardware,
> > or some SCHED_FIFO task preempting us here and running for 61 seconds without
> > yielding or something similarly weird.
> >
>
>
> Maybe I am being stupid here, but I don't follow this. They'll get a
> non-fatal error, that's all. Who else would be using spin_command? It's
> just a series of bytes to plug into the GD Rom registers, that's all.
>

After programming the registers we need to wait for the interrupt to clear
gd.pending, don't we?

<looks>

oh, I see. gd is a global singleton and we only support one command at a
time and one device. hrm.

> > > +
> > > +static int __devinit gdrom_set_interrupt_handlers(void)
> > > +{
> > > + int err;
> > > + init_waitqueue_head(&command_queue);
> > > + err = request_irq(HW_EVENT_GDROM_CMD, gdrom_command_interrupt, IRQF_DISABLED, "gdrom_command", &gd);
> > > + if (err)
> > > + return err;
> > > + init_waitqueue_head(&request_queue);
> >
> > You can initialise command_queue and request_queue at compile-time with
> > DECLARE_WAIT_QUEUE_HEAD().
> >
>
> Are you saying that is better?

Yup. Less source code, less object code, no startup-ordering issues.