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Groups > linux.kernel > #1281364
| From | Dmitry Torokhov <dmitry.torokhov@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros |
| Date | 2015-12-02 01:00 +0100 |
| Message-ID | <qB2ZZ-7VO-33@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <qB1rb-76P-7@gated-at.bofh.it> <qB1AR-79P-1@gated-at.bofh.it> <qB1Ky-7cT-13@gated-at.bofh.it> <qB1Ue-7g2-9@gated-at.bofh.it> <qB23T-7jj-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Dec 1, 2015 at 2:54 PM, Sinclair Yeh <syeh@vmware.com> wrote:
> Hi,
>
> On Tue, Dec 01, 2015 at 02:45:27PM -0800, Dmitry Torokhov wrote:
>> On Tue, Dec 1, 2015 at 2:32 PM, Sinclair Yeh <syeh@vmware.com> wrote:
>> > Hi,
>> >
>
> <snip>
>
>> >> > */
>> >> > -#define VMMOUSE_CMD(cmd, in1, out1, out2, out3, out4) \
>> >> > -({ \
>> >> > - unsigned long __dummy1, __dummy2; \
>> >> > - __asm__ __volatile__ ("inl %%dx" : \
>> >> > - "=a"(out1), \
>> >> > - "=b"(out2), \
>> >> > - "=c"(out3), \
>> >> > - "=d"(out4), \
>> >> > - "=S"(__dummy1), \
>> >> > - "=D"(__dummy2) : \
>> >> > - "a"(VMMOUSE_PROTO_MAGIC), \
>> >> > - "b"(in1), \
>> >> > - "c"(VMMOUSE_PROTO_CMD_##cmd), \
>> >> > - "d"(VMMOUSE_PROTO_PORT) : \
>> >> > - "memory"); \
>> >> > +#define VMMOUSE_CMD(cmd, in1, out1, out2, out3, out4) \
>> >> > +({ \
>> >> > + unsigned long __dummy1 = 0, __dummy2 = 0; \
>> >>
>> >> Why do we need to initialize dummies?
>> >
>> > Because for some commands those parameters to VMW_PORT() can be both
>> > input and outout.
>>
>> The vmmouse commands do not use them as input though, so it seems we
>> are simply wasting CPU cycles setting them to 0 just because we are
>> using the new VMW_PORT here. Why do we need to switch? What is the
>> benefit of doing this?
>
> There are two reasons. One is to make the code more readable and
> maintainable. Rather than having mostly similar inline assembly
> code sprinkled across multiple modules, we can just use the macros
> and document that.
At the cost of wasting cycles though :(.
Oh well, it is not like we are polling the backdoor here, so if you do
not care about a few wasted cycles I don't have to either ;)
>
> The second reason is this organization makes some on-going future
> development easier.
>
> Hope this helps.
>
> Sinclair
--
Dmitry
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[PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-01 23:20 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-12-01 23:30 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-01 23:40 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-12-01 23:50 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-02 00:00 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-12-02 01:00 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-02 01:10 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-02 03:20 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-02 16:40 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-02 17:00 +0100
Re: [Linux-graphics-maintainer] [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Thomas Hellstrom <thellstrom@vmware.com> - 2015-12-02 18:30 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-12-02 18:30 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-02 19:50 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-12-02 20:00 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros "Sinclair Yeh" <syeh@vmware.com> - 2015-12-02 20:10 +0100
Re: [Linux-graphics-maintainer] [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Thomas Hellstrom <thellstrom@vmware.com> - 2015-12-02 08:10 +0100
Re: [PATCH 3/6] Input: Update vmmouse.c to use the common VMW_PORT macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-02 01:10 +0100
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