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SubjectRe: [PATCHv2] parport: add parallel port support for SGI O2
Arnaud Giersch <arnaud.giersch@free.fr> wrote:
>
> From: Arnaud Giersch <arnaud.giersch@free.fr>
>
> Add support for the built-in parallel port on SGI O2 (a.k.a. IP32).
> Define a new configuration option: PARPORT_IP32. The module is named
> parport_ip32.
>
> Hardware support for SPP, EPP and ECP modes along with DMA support
> when available are currently implemented.

Nice looking driver. Big.

It does rather a lot of

if (foo) do_something();
whereas we prefer

if (foo)
do_something();
but if that was a blocker, we wouldn't have any drivers.

> +static void parport_ip32_dma_setup_context(unsigned int limit)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&parport_ip32_dma.lock, flags);
> + if (parport_ip32_dma.left > 0) {
> + volatile u64 __iomem *ctxreg = (parport_ip32_dma.ctx == 0) ?
> + &mace->perif.ctrl.parport.context_a :
> + &mace->perif.ctrl.parport.context_b;

Does this need to be volatile? writeq() should do the right thing.

> +static size_t parport_ip32_epp_read(void __iomem *eppreg,
> + struct parport *p, void *buf,
> + size_t len, int flags)
> +{
> + struct parport_ip32_private * const priv = p->physport->private_data;
> + size_t got;
> + parport_ip32_set_mode(p, ECR_MODE_EPP);
> + parport_ip32_data_reverse(p);
> + parport_ip32_write_control(p, DCR_nINIT);
> + if ((flags & PARPORT_EPP_FAST) && (len > 1)) {
> + readsb(eppreg, buf, len);

readsb() is a mips thing, and doesn't seem to be documented. What does it
do, and why does the driver use it (only) here?

> + writesb(eppreg, buf, len);

> +static unsigned int parport_ip32_fifo_wait_break(struct parport *p,
> + unsigned long expire)
> +{
> + cond_resched();
> + if (time_after(jiffies, expire)) {
> + printk(KERN_DEBUG PPIP32
> + "%s: FIFO write timed out\n", p->name);
> + return 1;
> + }
> + if (signal_pending(current)) {
> + printk(KERN_DEBUG PPIP32
> + "%s: Signal pending\n", p->name);
> + return 1;
> + }

This printk could be a bit noisy, if someone hoses a signal stream at a
printing program.

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