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    SubjectRe: [PATCH v2 10/17] drm/vram-helper: make drm_vram_mm_debugfs_init() return 0
    On Wed, Mar 18, 2020 at 08:10:43PM +0100, Daniel Vetter wrote:
    > On Wed, Mar 18, 2020 at 5:58 PM Greg KH <gregkh@linuxfoundation.org> wrote:
    > >
    > > On Wed, Mar 18, 2020 at 05:31:47PM +0100, Daniel Vetter wrote:
    > > > On Wed, Mar 18, 2020 at 5:03 PM Wambui Karuga <wambui.karugax@gmail.com> wrote:
    > > > >
    > > > >
    > > > >
    > > > > On Wed, 18 Mar 2020, Daniel Vetter wrote:
    > > > >
    > > > > > On Tue, Mar 10, 2020 at 04:31:14PM +0300, Wambui Karuga wrote:
    > > > > >> Since 987d65d01356 (drm: debugfs: make
    > > > > >> drm_debugfs_create_files() never fail), drm_debugfs_create_files() never
    > > > > >> fails and should return void. Therefore, remove its use as the
    > > > > >> return value of drm_vram_mm_debugfs_init(), and have the function
    > > > > >> return 0 directly.
    > > > > >>
    > > > > >> v2: have drm_vram_mm_debugfs_init() return 0 instead of void to avoid
    > > > > >> introducing build issues and build breakage.
    > > > > >>
    > > > > >> References: https://lists.freedesktop.org/archives/dri-devel/2020-February/257183.html
    > > > > >> Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
    > > > > >> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
    > > > > >> ---
    > > > > >> drivers/gpu/drm/drm_gem_vram_helper.c | 10 ++++------
    > > > > >> 1 file changed, 4 insertions(+), 6 deletions(-)
    > > > > >>
    > > > > >> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
    > > > > >> index 92a11bb42365..c8bcc8609650 100644
    > > > > >> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
    > > > > >> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
    > > > > >> @@ -1048,14 +1048,12 @@ static const struct drm_info_list drm_vram_mm_debugfs_list[] = {
    > > > > >> */
    > > > > >> int drm_vram_mm_debugfs_init(struct drm_minor *minor)
    > > > > >> {
    > > > > >> - int ret = 0;
    > > > > >> -
    > > > > >> #if defined(CONFIG_DEBUG_FS)
    > > > > >
    > > > > > Just noticed that this #if here is not needed, we already have a dummy
    > > > > > function for that case. Care to write a quick patch to remove it? On top
    > > > > > of this patch series here ofc, I'm in the processing of merging the entire
    > > > > > pile.
    > > > > >
    > > > > > Thanks, Daniel
    > > > > Hi Daniel,
    > > > > Without this check here, and compiling without CONFIG_DEBUG_FS, this
    > > > > function is run and the drm_debugfs_create_files() does not have access to
    > > > > the parameters also protected by an #if above this function. So the change
    > > > > throws an error for me. Is that correct?
    > > >
    > > > Hm right. Other drivers don't #ifdef out their debugfs file functions
    > > > ... kinda a bit disappointing that we can't do this in the neatest way
    > > > possible.
    > > >
    > > > Greg, has anyone ever suggested to convert the debugfs_create_file
    > > > function (and similar things) to macros that don't use any of the
    > > > arguments, and then also annotating all the static functions/tables as
    > > > __maybe_unused and let the compiler garbage collect everything?
    > > > Instead of explicit #ifdef in all the drivers ...
    > >
    > > No, no one has suggested that, having the functions be static inline
    > > should make it all "just work" properly if debugfs is not enabled. The
    > > variables will not be used, so the compiler should just optimize them
    > > away properly.
    > >
    > > No checks for CONFIG_DEBUG_FS should be needed anywhere in .c code.
    >
    > So the trouble with this one is that the static inline functions for
    > the debugfs file are wrapped in a #if too, and hence if we drop the
    > #if around the function call stuff won't compile. Should we drop all
    > the #if in the .c file and assume the compiler will remove all the
    > dead code and dead functions?

    Yes you should :)

    there should not be any need for #if in a .c file for debugfs stuff.

    thanks,

    greg k-h

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