[U-Boot] [PATCH 08/12] dm: stdio: Allow lazy probing of video devices

[Bin Meng]

Hi Simon,

On Mon, Oct 3, 2016 at 11:12 AM, Simon Glass <sjg at chromium.org> wrote:
> At present all video devices are probed on start-up. It would be better to
> probe a device only when it is needed. This can happen if it is referenced
> in the stdout environment variable, for example.
>
> Add support for this by searching for a suitable device when needed, probing
> it, and finding the stdio device it creates.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  common/stdio.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 63 insertions(+), 4 deletions(-)
>
> diff --git a/common/stdio.c b/common/stdio.c
> index f99cfe7..b58b3c7 100644
> --- a/common/stdio.c
> +++ b/common/stdio.c
> @@ -121,19 +121,76 @@ struct list_head* stdio_get_list(void)
>         return &(devs.list);
>  }
>
> +#ifdef CONFIG_DM_VIDEO
> +/**
> + * stdio_probe_device() - Find a device which provides the given stdio device
> + *
> + * This looks for a device of the given uclass which provides a particular
> + * stdio device. It is currently really only useful for UCLASS_VIDEO.
> + *
> + * Ultimately we want to be able to probe a device by its stdio name. At
> + * present devices register in their probe function (for video devices this
> + * is done in vidconsole_post_probe()) and we don't know what name they will
> + * use until they do so.
> + * TODO(sjg at chromium.org): We should be able to determine the name before
> + * probing, and probe the required device.
> + *
> + * @name:      stdio device name (e.g. "vidconsole")
> + * id:         Uclass ID of device to look for (e.g. UCLASS_VIDEO)
> + * @sdevp:     Returns stdout device, if found, else NULL
> + * @return 0 if found, -ENOENT if no device found with that name, other -ve
> + *        on other error
> + */
> +static int stdio_probe_device(const char *name, enum uclass_id id,
> +                             struct stdio_dev **sdevp)
> +{
> +       struct stdio_dev *sdev;
> +       struct udevice *dev;
> +       int seq, ret;
> +
> +       *sdevp = NULL;
> +       seq = trailing_strtoln(name, NULL);
> +       if (seq == -1)
> +               ret = uclass_first_device_err(id, &dev);
> +       else
> +               ret = uclass_get_device_by_seq(id, seq, &dev);
> +       if (ret) {
> +               debug("No %s device for seq %d (%s)\n", uclass_get_name(id),
> +                     seq, name);
> +               return ret;
> +       }
> +       /* The device should be be the last one registered */
> +       sdev = list_empty(&devs.list) ? NULL :
> +                       list_last_entry(&devs.list, struct stdio_dev, list);
> +       if (!sdev || strcmp(sdev->name, name)) {
> +               debug("Device '%s' did not register with stdio as '%s'\n",
> +                     dev->name, name);
> +               return -ENOENT;
> +       }
> +       *sdevp = sdev;
> +
> +       return 0;
> +}
> +#endif
> +
>  struct stdio_dev* stdio_get_by_name(const char *name)
>  {
>         struct list_head *pos;
> -       struct stdio_dev *dev;
> +       struct stdio_dev *sdev;
>
>         if(!name)
>                 return NULL;
>
>         list_for_each(pos, &(devs.list)) {
> -               dev = list_entry(pos, struct stdio_dev, list);
> -               if(strcmp(dev->name, name) == 0)
> -                       return dev;
> +               sdev = list_entry(pos, struct stdio_dev, list);
> +               if (strcmp(sdev->name, name) == 0)
> +                       return sdev;
>         }
> +#ifdef CONFIG_DM_VIDEO
> +       if (!strncmp(name, "vidconsole", 10) && !strchr(name, ',') &&

Why is strchr(name, ',') needed?

> +           !stdio_probe_device(name, UCLASS_VIDEO, &sdev))
> +               return sdev;
> +#endif
>
>         return NULL;
>  }
> @@ -282,6 +339,7 @@ int stdio_add_devices(void)
>  #endif
>  #endif
>  #ifdef CONFIG_DM_VIDEO
> +#ifndef CONFIG_SYS_CONSOLE_IS_IN_ENV

Wy adding CONFIG_SYS_CONSOLE_IS_IN_ENV check?

>         struct udevice *vdev;
>  # ifndef CONFIG_DM_KEYBOARD
>         int ret;
> @@ -293,6 +351,7 @@ int stdio_add_devices(void)
>                 ;
>         if (ret)
>                 printf("%s: Video device failed (ret=%d)\n", __func__, ret);
> +#endif /* !CONFIG_SYS_CONSOLE_IS_IN_ENV */
>  #else
>  # if defined(CONFIG_LCD)
>         drv_lcd_init ();
> --

Regards,
Bin