linux-kernel - Re: [PATCH] drm/nouveau/debugfs: Simplify character output in nouveau_debugfs_vbios

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Message-ID: <147bde68-2b66-4e0c-890d-30571a99eee1@wanadoo.fr>
Date: Tue, 23 Jul 2024 18:57:44 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Ilia Mirkin <imirkin@...m.mit.edu>
Cc: nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 kernel-janitors@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
 Danilo Krummrich <dakr@...hat.com>, David Airlie <airlied@...il.com>,
 Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
 LKML <linux-kernel@...r.kernel.org>, Markus Elfring <Markus.Elfring@....de>
Subject: Re: [PATCH] drm/nouveau/debugfs: Simplify character output in
 nouveau_debugfs_vbios_image()

Le 15/07/2024 à 15:15, Ilia Mirkin a écrit :
> On Mon, Jul 15, 2024 at 7:49 AM Markus Elfring <Markus.Elfring@....de> wrote:
>>
>> From: Markus Elfring <elfring@...rs.sourceforge.net>
>> Date: Mon, 15 Jul 2024 13:36:54 +0200
>>
>> Single characters should be put into a sequence.
>> Thus use the corresponding function “seq_putc” for one selected call.
>>
>> This issue was transformed by using the Coccinelle software.
>>
>> Suggested-by: Christophe Jaillet <christophe.jaillet@...adoo.fr>
>> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
>> ---
>>   drivers/gpu/drm/nouveau/nouveau_debugfs.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_debugfs.c b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
>> index e83db051e851..931b62097366 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_debugfs.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_debugfs.c
>> @@ -42,7 +42,7 @@ nouveau_debugfs_vbios_image(struct seq_file *m, void *data)
>>          int i;
>>
>>          for (i = 0; i < drm->vbios.length; i++)
>> -               seq_printf(m, "%c", drm->vbios.data[i]);
>> +               seq_putc(m, drm->vbios.data[i]);
> 
> Is there some reason this whole thing isn't just
> 
> seq_write(m, drm->vbios.data, drm->vbios.length)

Hi,

I don't know if my answer is relevant or not here but:
	for () seq_putc();	==> will fill 'm' with everything that fits in
and
	seq_write()		==> is all or nothing. So if 'm' is too small, then 
nothing will be appended.

I've not looked at the calling tree, but I would expect 'm' to be able 
to have PAGE_SIZE chars, so most probably 4096.

And having gpu + "vbios.rom", I would expect it to be bigger than 4096.

If I'm correct, then changing for seq_write() would just show... nothing.


I don't know if it can happen., but testing should be easy enough to 
figure it out.

just my 2c.

CJ



> 
>>          return 0;
>>   }
>>
>> --
>> 2.45.2
>>
> 
>