Re: [yocto] [psplash][PATCH 1/1] psplash-fb: Avoid racing issues on reading fb0

["Khem Raj" <raj.khem@gmail.com>]

On 2/20/20 9:58 AM, Andrei Gherzan wrote:
> Hi,
> 
> On Fri, Feb 14, 2020 at 7:32 AM Khem Raj <raj.khem@gmail.com 
> <mailto:raj.khem@gmail.com>> wrote:
> 
>     On 2/13/20 2:30 AM, Andrei Gherzan wrote:
>      > When starting psplash as early as possible in the boot process,
>     the fb
>      > device node might not be ready. This patch adds a loop on reading the
>      > fb0 device with a timeout of 5 seconds.
>      >
>      > Signed-off-by: Andrei Gherzan <andrei@gherzan.ro
>     <mailto:andrei@gherzan.ro>>
>      > ---
>      >   psplash-fb.c | 5 ++++-
>      >   1 file changed, 4 insertions(+), 1 deletion(-)
>      >
>      > diff --git a/psplash-fb.c b/psplash-fb.c
>      > index 6603572..6700a3b 100644
>      > --- a/psplash-fb.c
>      > +++ b/psplash-fb.c
>      > @@ -137,6 +137,7 @@ psplash_fb_new (int angle, int fbdev_id)
>      >     struct fb_fix_screeninfo fb_fix;
>      >     int                      off;
>      >     char                     fbdev[9] = "/dev/fb0";
>      > +  int retries = 0;
>      >
>      >     PSplashFB *fb = NULL;
>      >
>      > @@ -156,7 +157,9 @@ psplash_fb_new (int angle, int fbdev_id)
>      >
>      >     fb->fd = -1;
>      >
>      > -  if ((fb->fd = open (fbdev, O_RDWR)) < 0)
>      > +  while ((fb->fd = open(fbdev, O_RDWR)) < 0 && retries++ <= 100)
>      > +       usleep(50000);
>      > +  if (fb->fd < 0)
> 
>     i wonder if there should be a different way to ensure this dependency
>     perhaps sd_notify for systemd or udev notification maybe ..
> 
> 
> That makes sense. The only issue is that in my use-case, initramfs 
> doesn't have systemd. And usually, you will be wanting to run a splash 
> way before any init system. What is your proposal with udev 
> notifications? Can you expand that?
> 

something like 
https://www.tecmint.com/udev-for-device-detection-management-in-linux/


> Regards,
> Andrei