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

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Message-ID: <CAHp75VcRqxb+ov2KoaYv_U0sR_Hpt7dthE6v1DikABW6iQ-zMQ@mail.gmail.com>
Date:	Sat, 28 Nov 2015 21:18:13 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Dave Penkler <dpenkler@...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 7:41 PM, Dave Penkler <dpenkler@...il.com> wrote:
> 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.

Yes, fine by me, thanks for patience.

-- 
With Best Regards,
Andy Shevchenko
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