linux-kernel - Re: [PATCH] drm/xe: replace basename() with portable strrchr()

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Message-ID: <v5j6nxynzvvlcxu3m3mkeyjv5dlozzp7ixkgc6u6hdzh7en6jh@zvzqm5n7njfd>
Date: Thu, 21 Aug 2025 16:00:33 -0500
From: Lucas De Marchi <lucas.demarchi@...el.com>
To: Carlos Llamas <cmllamas@...gle.com>
CC: Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>, Matt Atwood <matthew.s.atwood@...el.com>,
	<kernel-team@...roid.com>, <linux-kernel@...r.kernel.org>, "open list:INTEL
 DRM XE DRIVER (Lunar Lake and newer)" <intel-xe@...ts.freedesktop.org>, "open
 list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/xe: replace basename() with portable strrchr()

On Wed, Aug 20, 2025 at 11:05:47PM +0000, Carlos Llamas wrote:
>On Wed, Aug 20, 2025 at 04:15:47PM -0500, Lucas De Marchi wrote:
>> On Wed, Aug 20, 2025 at 08:16:11PM +0000, Carlos Llamas wrote:
>> > Commit b0a2ee5567ab ("drm/xe: prepare xe_gen_wa_oob to be multi-use")
>> > introduced a call to basename(). The GNU version of this function is not
>> > portable and fails to build with alternative libc implementations like
>> > musl or bionic. This causes the following build error:
>> >
>> >  drivers/gpu/drm/xe/xe_gen_wa_oob.c:130:12: error: assignment to ‘const char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
>> >    130 |         fn = basename(fn);
>> >        |            ^
>> >
>> > While a POSIX version of basename() could be used, it would require a
>> > separate header plus the behavior differs from GNU version in that it
>> > might modify its argument. Not great.
>> >
>> > Instead replace basename() with a strrchr() based implementation which
>> > provides the same functionality and avoid portability issues.
>> >
>> > Fixes: b0a2ee5567ab ("drm/xe: prepare xe_gen_wa_oob to be multi-use")
>> > Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
>> > ---
>> > drivers/gpu/drm/xe/xe_gen_wa_oob.c | 4 +++-
>> > 1 file changed, 3 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/gpu/drm/xe/xe_gen_wa_oob.c b/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>> > index 6581cb0f0e59..0a94a045bcea 100644
>> > --- a/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>> > +++ b/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>> > @@ -125,9 +125,11 @@ static int parse(FILE *input, FILE *csource, FILE *cheader, char *prefix)
>> >
>> > static int fn_to_prefix(const char *fn, char *prefix, size_t size)
>> > {
>> > +	const char *base;
>> > 	size_t len;
>> >
>> > -	fn = basename(fn);
>> > +	base = strrchr(fn, '/');
>> > +	fn = base ? base + 1 : fn;
>>
>> I think just a xbasename() helper like we've added in kmod would be
>> preferred:
>> https://github.com/kmod-project/kmod/commit/11eb9bc67c319900ab00523997323a97d2d08ad2
>>
>> Alternativelly add it somewhere that can be shared across the userspace
>> tools in the kernel tree to fix the mess that we have here:
>>
>> 	git grep basename -- tools/**.c
>>
>
>This sounds like a nice idea. However, there is no "centralized" shared
>includes/ across the userspace tools that I'm aware of?
>
>> Some dup the arg simply to be able to use the libgen.h version, some use
>> one or the other on purpose, etc etc.
>>
>
>Yeah, and I can force the POSIX version if you prefer. I just personally
>think the strrchr() alternative ends up being simpler.

IMO the POSIX version is horrible. Let's add a xbasename() in this
xe_gen_wa_oob.c and use it:

/*
  * Avoid the libgen.h vs string.h differences or lack thereof, just use
  * our own.
  */
static const char *xbasename(const char *s)
{
	const char *p = strrchr(s, '/');
	return p ? p + 1 : s;
}

static int fn_to_prefix(const char *fn, char *prefix, size_t size)
{
...
	fn = xbasename(fn);
...
}

Lucas De Marchi