[Nouveau] [PATCH 1/2] nouveau/bl: Assign different names to interfaces

[Pierre Moreau]

On 11:06 AM - Apr 15 2016, Ilia Mirkin wrote:
> On Fri, Apr 15, 2016 at 10:57 AM, Pierre Moreau <pierre.morrow at free.fr> wrote:
> > Currently, every backlight interface created by Nouveau uses the same name,
> > nv_backlight. This leads to a sysfs warning as it tries to create an already
> > existing folder. This patch adds a incremented number to the name, but keeps
> > the initial name as nv_backlight, to avoid possibly breaking userspace; the
> > second interface will be named nv_backlight1, and so on.
> >
> > Fixes: fdo#86539
> > Signed-off-by: Pierre Moreau <pierre.morrow at free.fr>
> > ---
> >  drm/nouveau/nouveau_backlight.c | 35 +++++++++++++++++++++++++++++++++--
> >  1 file changed, 33 insertions(+), 2 deletions(-)
> >
> > diff --git a/drm/nouveau/nouveau_backlight.c b/drm/nouveau/nouveau_backlight.c
> > index 89eb460..914e2cb 100644
> > --- a/drm/nouveau/nouveau_backlight.c
> > +++ b/drm/nouveau/nouveau_backlight.c
> > @@ -36,6 +36,10 @@
> >  #include "nouveau_reg.h"
> >  #include "nouveau_encoder.h"
> >
> > +static atomic_t bl_interfaces_nb = { 0 };
> 
> static data is initialized to 0, this should be unnecessary.

I didn’t know that. But on the other hand, I like having it explicit, and it
should not add any overhead.

> 
> I'd also call it "backlights" or something like that. No need for
> multiple words...

I prefer to use a plural noun when talking about a container of those nouns,
rathter than a counter of those nouns. But I’ll change it.

> 
> > +
> > +static char* nouveau_get_backlight_name(void);
> 
> Please organize the code to avoid forward declarations.
> 
> > +
> >  static int
> >  nv40_get_intensity(struct backlight_device *bd)
> >  {
> > @@ -74,6 +78,7 @@ nv40_backlight_init(struct drm_connector *connector)
> >         struct nvif_object *device = &drm->device.object;
> >         struct backlight_properties props;
> >         struct backlight_device *bd;
> > +       char* backlight_name = NULL;
> >
> >         if (!(nvif_rd32(device, NV40_PMC_BACKLIGHT) & NV40_PMC_BACKLIGHT_MASK))
> >                 return 0;
> > @@ -81,8 +86,14 @@ nv40_backlight_init(struct drm_connector *connector)
> >         memset(&props, 0, sizeof(struct backlight_properties));
> >         props.type = BACKLIGHT_RAW;
> >         props.max_brightness = 31;
> > -       bd = backlight_device_register("nv_backlight", connector->kdev, drm,
> > +       backlight_name = nouveau_get_backlight_name();
> > +       bd = backlight_device_register(backlight_name , connector->kdev, drm,
> >                                        &nv40_bl_ops, &props);
> > +
> > +       // backlight_device_register() makes a copy
> > +       kfree(backlight_name);
> > +       backlight_name = NULL;
> > +
> >         if (IS_ERR(bd))
> >                 return PTR_ERR(bd);
> >         drm->backlight = bd;
> > @@ -182,6 +193,7 @@ nv50_backlight_init(struct drm_connector *connector)
> >         struct backlight_properties props;
> >         struct backlight_device *bd;
> >         const struct backlight_ops *ops;
> > +       char* backlight_name = NULL;
> >
> >         nv_encoder = find_encoder(connector, DCB_OUTPUT_LVDS);
> >         if (!nv_encoder) {
> > @@ -203,8 +215,14 @@ nv50_backlight_init(struct drm_connector *connector)
> >         memset(&props, 0, sizeof(struct backlight_properties));
> >         props.type = BACKLIGHT_RAW;
> >         props.max_brightness = 100;
> > -       bd = backlight_device_register("nv_backlight", connector->kdev,
> > +       backlight_name = nouveau_get_backlight_name();
> > +       bd = backlight_device_register(backlight_name, connector->kdev,
> >                                        nv_encoder, ops, &props);
> > +
> > +       // backlight_device_register() makes a copy
> > +       kfree(backlight_name);
> > +       backlight_name = NULL;
> > +
> >         if (IS_ERR(bd))
> >                 return PTR_ERR(bd);
> >
> > @@ -252,3 +270,16 @@ nouveau_backlight_exit(struct drm_device *dev)
> >                 drm->backlight = NULL;
> >         }
> >  }
> > +
> > +static char*
> > +nouveau_get_backlight_name(void)
> > +{
> > +       // 12 chars for "nv_backlight" + 2 for two digits number + 1 for '\0'
> > +       char* backlight_name = (char*)kmalloc(sizeof(char[15]), GFP_KERNEL);
> 
> Making this stack-allocated in the caller would be so much simpler...

--" I was planning to use a dynamic size to allow numbers bigger than 99, and
lesser than 10, but stopped midway through the process. I’ll revert to a plain
stack-allocated.

> 
> > +       const int nb = atomic_inc_return(&bl_interfaces_nb) - 1;
> 
> This kinda sucks if you reload nouveau a bunch. How about using an
> "ida". Have a look in drivers/gpu/drm/drm_crtc.c for how I use that
> one.

Yeah, I’m not really fond of that part. I’ll have a look at drm_crtc.c!

Pierre


> 
> > +       if (nb > 0 && nb < 100)
> > +               sprintf(backlight_name, "nv_backlight%d", nb);
> > +       else
> > +               sprintf(backlight_name, "nv_backlight");
> > +       return backlight_name;
> > +}
> > --
> > 2.8.0
> >
> > _______________________________________________
> > Nouveau mailing list
> > Nouveau at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/nouveau
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