[U-Boot] [PATCH 1/2] dm: core: Add uclass_first_device_err() to return a valid device

[Bin Meng]

Hi Simon,

On Fri, Feb 12, 2016 at 4:23 AM, Simon Glass <sjg at chromium.org> wrote:
> A common pattern is to call uclass_first_device() and then check if it
> actually returns a device. Add a new function which does this, returning
> an error if there are no devices in that uclass.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  drivers/core/uclass.c | 13 +++++++++++++
>  include/dm/uclass.h   | 15 +++++++++++++--
>  2 files changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
> index 12095e7..1141ce1 100644
> --- a/drivers/core/uclass.c
> +++ b/drivers/core/uclass.c
> @@ -401,6 +401,19 @@ int uclass_first_device(enum uclass_id id, struct udevice **devp)
>         return uclass_get_device_tail(dev, ret, devp);
>  }
>
> +int uclass_first_device_err(enum uclass_id id, struct udevice **devp)

Or maybe another way is to change uclass_first_device() behavior to
return -ENODEV if device is not found? (move the return value test
logic into uclass_first_device)

> +{
> +       int ret;
> +
> +       ret = uclass_first_device(id, devp);
> +       if (ret)
> +               return ret;
> +       else if (!*devp)
> +               return -ENODEV;
> +
> +       return 0;
> +}
> +
>  int uclass_next_device(struct udevice **devp)
>  {
>         struct udevice *dev = *devp;
> diff --git a/include/dm/uclass.h b/include/dm/uclass.h
> index bfbd27a..fd368b6 100644
> --- a/include/dm/uclass.h
> +++ b/include/dm/uclass.h
> @@ -200,18 +200,29 @@ int uclass_get_device_by_phandle(enum uclass_id id, struct udevice *parent,
>   *
>   * @id: Uclass ID to look up
>   * @devp: Returns pointer to the first device in that uclass, or NULL if none
> - * @return 0 if OK (found or not found), -1 on error
> + * @return 0 if OK (found or not found), other -ve on error
>   */
>  int uclass_first_device(enum uclass_id id, struct udevice **devp);
>
>  /**
> + * uclass_first_device_err() - Get the first device in a uclass
> + *
> + * The device returned is probed if necessary, and ready for use
> + *
> + * @id: Uclass ID to look up
> + * @devp: Returns pointer to the first device in that uclass, or NULL if none
> + * @return 0 if found, -ENODEV if not found, other -ve on error
> + */
> +int uclass_first_device_err(enum uclass_id id, struct udevice **devp);
> +
> +/**
>   * uclass_next_device() - Get the next device in a uclass
>   *
>   * The device returned is probed if necessary, and ready for use
>   *
>   * @devp: On entry, pointer to device to lookup. On exit, returns pointer
>   * to the next device in the same uclass, or NULL if none
> - * @return 0 if OK (found or not found), -1 on error
> + * @return 0 if OK (found or not found), other -ve on error
>   */
>  int uclass_next_device(struct udevice **devp);
>
> --

Regards,
Bin