Mailing List Archive: Linux: Kernel

[PATCH] ata: Clean up hard coded array size calculation.

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tfransosi at gmail

Nov 8, 2009, 11:30 AM

Post #1 of 15 (437 views)
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[PATCH] ata: Clean up hard coded array size calculation.

Use ARRAY_SIZE macro of kernel api instead.

Signed-off-by: Thiago Farina <tfransosi [at] gmail>
---
drivers/ata/sata_mv.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 6f5093b..a8a7be0 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct ata_queued_cmd *qc)
int err = 0;

ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
- err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
+ err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
if (err)
return err;

--
1.6.5.2.150.g1b52a

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tfransosi at gmail

Nov 8, 2009, 11:45 AM

Post #2 of 15 (428 views)
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Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On Sun, Nov 8, 2009 at 5:30 PM, Thiago Farina <tfransosi [at] gmail> wrote:
> Use ARRAY_SIZE macro of kernel api instead.
>
> Signed-off-by: Thiago Farina <tfransosi [at] gmail>
Reported-by: Robert P. J. Day <rpjday [at] crashcourse>
> ---
> drivers/ata/sata_mv.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> index 6f5093b..a8a7be0 100644
> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct ata_queued_cmd *qc)
> int err = 0;
>
> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
> if (err)
> return err;
>
> --
> 1.6.5.2.150.g1b52a
>
>
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liml at rtr

Nov 9, 2009, 9:00 PM

Post #3 of 15 (412 views)
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Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

Thiago Farina wrote:
> Use ARRAY_SIZE macro of kernel api instead.
>
> Signed-off-by: Thiago Farina <tfransosi [at] gmail>
> ---
> drivers/ata/sata_mv.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> index 6f5093b..a8a7be0 100644
> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct ata_queued_cmd *qc)
> int err = 0;
>
> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
> if (err)
> return err;
>
..

What's the point of this ?

There is no "hardcoded array size" there to begin with,
and using that silly macro obscures the actual calculation.

So now, instead of being able to verify correctness at a glance,
I have to go off and research some silly macro and verify that
it does the right thing.

Kind of like all of those "typedef structs" that are abhored around here.

-ml
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bzolnier at gmail

Nov 10, 2009, 7:51 AM

Post #4 of 15 (409 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On Tuesday 10 November 2009 06:00:19 Mark Lord wrote:
> Thiago Farina wrote:
> > Use ARRAY_SIZE macro of kernel api instead.
> >
> > Signed-off-by: Thiago Farina <tfransosi [at] gmail>
> > ---
> > drivers/ata/sata_mv.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> > index 6f5093b..a8a7be0 100644
> > --- a/drivers/ata/sata_mv.c
> > +++ b/drivers/ata/sata_mv.c
> > @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct ata_queued_cmd *qc)
> > int err = 0;
> >
> > ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
> > - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
> > + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
> > if (err)
> > return err;
> >
> ..
>
> What's the point of this ?
>
> There is no "hardcoded array size" there to begin with,
> and using that silly macro obscures the actual calculation.
>
> So now, instead of being able to verify correctness at a glance,

I kindly disagree here. ARRAY_SIZE makes code smaller and prevents
subtle bugs in the more complex situations once you learn to always
use it.

[. Using ARRAY_SIZE you no longer have to verify anything and person
looking at the code (which not necessarily is the original author)
immediately knows what was the author's intention. ]

> I have to go off and research some silly macro and verify that
> it does the right thing.

You did it already and the macro name is quite descriptive so you
may as well just ACK the patch now.. ;)

--
Bartlomiej Zolnierkiewicz
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penberg at cs

Nov 10, 2009, 8:08 AM

Post #5 of 15 (409 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On Tue, Nov 10, 2009 at 5:51 PM, Bartlomiej Zolnierkiewicz
<bzolnier [at] gmail> wrote:
>> I have to go off and research some silly macro and verify that
>> it does the right thing.
>
> You did it already and the macro name is quite descriptive so you
> may as well just ACK the patch now.. ;)

Indeed. We use the "silly macro" everywhere in the kernel for code clarity.
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liml at rtr

Nov 11, 2009, 2:37 PM

Post #6 of 15 (404 views)
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Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

Pekka Enberg wrote:
> On Tue, Nov 10, 2009 at 5:51 PM, Bartlomiej Zolnierkiewicz
> <bzolnier [at] gmail> wrote:
>>> I have to go off and research some silly macro and verify that
>>> it does the right thing.
>> You did it already and the macro name is quite descriptive so you
>> may as well just ACK the patch now.. ;)
>
> Indeed. We use the "silly macro" everywhere in the kernel for code clarity.
..

Looks like unnecessary churn and obfuscation to me.

-ml
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tfransosi at gmail

Nov 11, 2009, 2:50 PM

Post #7 of 15 (404 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On Wed, Nov 11, 2009 at 8:37 PM, Mark Lord <liml [at] rtr> wrote:
> Looks like unnecessary churn and obfuscation to me.

Obfuscation? Are you saying that just because you wrote this code? So
what is the usage of a macro? I think you are having a defensive
position here.

The macro is self-explanatory, ARRAY_SIZE, so the macro gives you the
*size* of the array. You don't need to know how that is done, if you
want, just go to the declaration of the macro.
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jgarzik at pobox

Nov 11, 2009, 3:10 PM

Post #8 of 15 (404 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On 11/10/2009 12:00 AM, Mark Lord wrote:
> Thiago Farina wrote:
>> Use ARRAY_SIZE macro of kernel api instead.
>>
>> Signed-off-by: Thiago Farina <tfransosi [at] gmail>
>> ---
>> drivers/ata/sata_mv.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
>> index 6f5093b..a8a7be0 100644
>> --- a/drivers/ata/sata_mv.c
>> +++ b/drivers/ata/sata_mv.c
>> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct
>> ata_queued_cmd *qc)
>> int err = 0;
>>
>> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
>> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
>> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
>> if (err)
>> return err;
>>
> ..
>
> What's the point of this ?
>
> There is no "hardcoded array size" there to begin with,
> and using that silly macro obscures the actual calculation.
>
> So now, instead of being able to verify correctness at a glance,
> I have to go off and research some silly macro and verify that
> it does the right thing.

It is a standard cleanup for all kernel code, and it does make the code
more readable to the casual reader / quick skimmer.

Jeff

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liml at rtr

Nov 12, 2009, 3:53 PM

Post #9 of 15 (395 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

Thiago Farina wrote:
> On Wed, Nov 11, 2009 at 8:37 PM, Mark Lord <liml [at] rtr> wrote:
>> Looks like unnecessary churn and obfuscation to me.
>
> Obfuscation? Are you saying that just because you wrote this code? So
> what is the usage of a macro? I think you are having a defensive
> position here.
..

No, actually I believe Jeff wrote that particular line of code.

Cheers
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jgarzik at pobox

Nov 12, 2009, 4:25 PM

Post #10 of 15 (394 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On 11/12/2009 06:53 PM, Mark Lord wrote:
> Thiago Farina wrote:
>> On Wed, Nov 11, 2009 at 8:37 PM, Mark Lord <liml [at] rtr> wrote:
>>> Looks like unnecessary churn and obfuscation to me.
>>
>> Obfuscation? Are you saying that just because you wrote this code? So
>> what is the usage of a macro? I think you are having a defensive
>> position here.
> ..
>
> No, actually I believe Jeff wrote that particular line of code.

You know, Linus actually invented a command for people who enjoy this
game... ;)

git blame drivers/ata/sata_mv.c

shows each line of code, and metadata about each line such as commit id
and author name.

Jeff

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tfransosi at gmail

Nov 12, 2009, 4:41 PM

Post #11 of 15 (394 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On Thu, Nov 12, 2009 at 10:25 PM, Jeff Garzik <jgarzik [at] pobox> wrote:
> On 11/12/2009 06:53 PM, Mark Lord wrote:
>>
>> Thiago Farina wrote:
>>>
>>> On Wed, Nov 11, 2009 at 8:37 PM, Mark Lord <liml [at] rtr> wrote:
>>>>
>>>> Looks like unnecessary churn and obfuscation to me.
>>>
>>> Obfuscation? Are you saying that just because you wrote this code? So
>>> what is the usage of a macro? I think you are having a defensive
>>> position here.
>>
>> ..
>>
>> No, actually I believe Jeff wrote that particular line of code.
>
> You know, Linus actually invented a command for people who enjoy this
> game... ;)
>
> git blame drivers/ata/sata_mv.c
>
> shows each line of code, and metadata about each line such as commit id and
> author name.

Sure, and I ran this command before saying that Mark wrote this code.
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liml at rtr

Nov 13, 2009, 7:23 PM

Post #12 of 15 (385 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

Thiago Farina wrote:
> On Thu, Nov 12, 2009 at 10:25 PM, Jeff Garzik <jgarzik [at] pobox> wrote:
>> On 11/12/2009 06:53 PM, Mark Lord wrote:
>>> Thiago Farina wrote:
>>>> On Wed, Nov 11, 2009 at 8:37 PM, Mark Lord <liml [at] rtr> wrote:
>>>>> Looks like unnecessary churn and obfuscation to me.
>>>> Obfuscation? Are you saying that just because you wrote this code? So
>>>> what is the usage of a macro? I think you are having a defensive
>>>> position here.
>>> ..
>>>
>>> No, actually I believe Jeff wrote that particular line of code.
>> You know, Linus actually invented a command for people who enjoy this
>> game... ;)
>>
>> git blame drivers/ata/sata_mv.c
>>
>> shows each line of code, and metadata about each line such as commit id and
>> author name.
>
> Sure, and I ran this command before saying that Mark wrote this code.
..

I'm probably just the last chap to change the indentation on it.
It really doesn't look like my style to me. ;)

There were two authors before me there, and that line looks like one of theirs. :)

Cheers
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jgarzik at pobox

Nov 16, 2009, 7:17 PM

Post #13 of 15 (356 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On 11/08/2009 02:30 PM, Thiago Farina wrote:
> Use ARRAY_SIZE macro of kernel api instead.
>
> Signed-off-by: Thiago Farina<tfransosi [at] gmail>
> ---
> drivers/ata/sata_mv.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> index 6f5093b..a8a7be0 100644
> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct ata_queued_cmd *qc)
> int err = 0;
>
> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
> if (err)

applied

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tfransosi at gmail

Nov 20, 2009, 11:15 AM

Post #14 of 15 (346 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

Hi Jeff,

On Tue, Nov 17, 2009 at 1:17 AM, Jeff Garzik <jgarzik [at] pobox> wrote:
> On 11/08/2009 02:30 PM, Thiago Farina wrote:
>>
>> Use ARRAY_SIZE macro of kernel api instead.
>>
>> Signed-off-by: Thiago Farina<tfransosi [at] gmail>
>> ---
>> drivers/ata/sata_mv.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
>> index 6f5093b..a8a7be0 100644
>> --- a/drivers/ata/sata_mv.c
>> +++ b/drivers/ata/sata_mv.c
>> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct
>> ata_queued_cmd *qc)
>> int err = 0;
>>
>> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
>> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
>> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
>> if (err)
>
> applied

Was it applied to this tree
http://git.kernel.org/?p=linux/kernel/git/jgarzik/libata-dev.git?
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jgarzik at pobox

Nov 20, 2009, 2:05 PM

Post #15 of 15 (346 views)
Permalink

Re: [PATCH] ata: Clean up hard coded array size calculation. [In reply to]

On 11/20/2009 02:15 PM, Thiago Farina wrote:
> Hi Jeff,
>
> On Tue, Nov 17, 2009 at 1:17 AM, Jeff Garzik<jgarzik [at] pobox> wrote:
>> On 11/08/2009 02:30 PM, Thiago Farina wrote:
>>>
>>> Use ARRAY_SIZE macro of kernel api instead.
>>>
>>> Signed-off-by: Thiago Farina<tfransosi [at] gmail>
>>> ---
>>> drivers/ata/sata_mv.c | 2 +-
>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
>>> index 6f5093b..a8a7be0 100644
>>> --- a/drivers/ata/sata_mv.c
>>> +++ b/drivers/ata/sata_mv.c
>>> @@ -2217,7 +2217,7 @@ static unsigned int mv_qc_issue_fis(struct
>>> ata_queued_cmd *qc)
>>> int err = 0;
>>>
>>> ata_tf_to_fis(&qc->tf, link->pmp, 1, (void *)fis);
>>> - err = mv_send_fis(ap, fis, sizeof(fis) / sizeof(fis[0]));
>>> + err = mv_send_fis(ap, fis, ARRAY_SIZE(fis));
>>> if (err)
>>
>> applied
>
> Was it applied to this tree
> http://git.kernel.org/?p=linux/kernel/git/jgarzik/libata-dev.git?

Yes.

Jeff

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