linux-kernel - Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488 READ_STATUS

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Date:	Sat, 28 Nov 2015 18:41:18 +0100
From:	Dave Penkler <dpenkler@...il.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	peter.chen@...escale.com, teuniz@...il.com,
	USB <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488
 READ_STATUS_BYTE operation.

On Sat, Nov 28, 2015 at 04:57:47PM +0200, Andy Shevchenko wrote:
> On Sat, Nov 28, 2015 at 1:55 PM, Dave Penkler <dpenkler@...il.com> wrote:
> > On Wed, Nov 25, 2015 at 10:38:39PM +0200, Andy Shevchenko wrote:
> >> On Wed, Nov 25, 2015 at 11:18 AM, Dave Penkler <dpenkler@...il.com> wrote:
> >> > On Sun, Nov 22, 2015 at 12:32:41PM +0200, Andy Shevchenko wrote:
> >> >> On Sun, Nov 22, 2015 at 11:19 AM, Dave Penkler <dpenkler@...il.com> wrote:
> >> >> > On Wed, Nov 18, 2015 at 11:55:27AM +0200, Andy Shevchenko wrote:
> >> >> >> On Wed, Nov 18, 2015 at 10:37 AM, Dave Penkler <dpenkler@...il.com> wrote:
> 
> Thank you for an update!
> 
> >> >> >> > +       switch (status) {
> >> >> >> > +       case 0: /* SUCCESS */
> >> >> >> > +               if (data->iin_buffer[0] & 0x80) {
> >> >> >> > +                       /* check for valid STB notification */
> >> >> >> > +                       if ((data->iin_buffer[0] & 0x7f) > 1) {
> 
> How can I miss that there are two conditionals in a sequence and
> moreover for the same data?!

Sorry, my fault, it is the combination of patch 1 and 2

> That might explain the optimization done by compiler.
> 
> So, could it be transformed to simple one condition
>    if (data->iin_buffer[0] > 0x81 /* 129 */) {
> ?

OK so now for patch 1 and 2 we have:

	switch (status) {
	case 0: /* SUCCESS */
		/* PATCH 1 check for valid STB notification */
		if (data->iin_buffer[0] > 0x81) {
			data->bNotify1 = data->iin_buffer[0];
			data->bNotify2 = data->iin_buffer[1];
			atomic_set(&data->iin_data_valid, 1);
			wake_up_interruptible(&data->waitq);
			goto exit;
		}
		/* PATCH 2 check for SRQ notification */
		if (data->iin_buffer[0] == 0x81) {
			if (data->fasync)
				kill_fasync(&data->fasync,
					SIGIO, POLL_IN);

			atomic_set(&data->srq_asserted, 1);
			wake_up_interruptible(&data->waitq);
			goto exit;
		}


I'll push a new set if you are OK with this.
cheers,
-Dave
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