linux-kernel - Re: [PATCH v1 2/3] auxdisplay: ht16k33: Make use of device_get_match

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Message-ID: <Y/UD3HWNy8uKYShC@smile.fi.intel.com>
Date:   Tue, 21 Feb 2023 19:48:12 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Robin van der Gracht <robin@...tonic.nl>
Cc:     "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Raul E Rangel <rrangel@...omium.org>,
        Wolfram Sang <wsa@...nel.org>, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-usb@...r.kernel.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v1 2/3] auxdisplay: ht16k33: Make use of
 device_get_match_data()

On Tue, Feb 21, 2023 at 05:10:00PM +0100, Robin van der Gracht wrote:
> On 2023-02-21 14:40, Andy Shevchenko wrote:
> > On Tue, Feb 21, 2023 at 03:33:06PM +0200, Andy Shevchenko wrote:
> > > Switching to use device_get_match_data() helps getting of
> > > i2c_of_match_device() API.

...

> > > -	id = i2c_of_match_device(dev->driver->of_match_table, client);
> > > -	if (id)
> > > -		priv->type = (uintptr_t)id->data;
> > > +	priv->type = (uintptr_t)device_get_match_data(dev);
> > 
> > Looking closer the I²C ID table should provide DISP_MATRIX to keep
> > default and this needs to be not dropped.
> > 
> > So, the question is what to do with unknown type then, return -EINVAL
> > from probe()?
> 
> If you leave out your addition of the DISP_UNKNOWN type, the default type
> will be DISP_MATRIX if no match is found, which is as it is now.
> 
> In that case the following change should suffice:
> 
> @@ -713,7 +715,6 @@ static int ht16k33_seg_probe(struct device *dev, struct
> ht16k33_priv *priv,
>  static int ht16k33_probe(struct i2c_client *client)
>  {
>      struct device *dev = &client->dev;
> -    const struct of_device_id *id;
>      struct ht16k33_priv *priv;
>      uint32_t dft_brightness;
>      int err;
> @@ -728,9 +729,8 @@ static int ht16k33_probe(struct i2c_client *client)
>          return -ENOMEM;
> 
>      priv->client = client;
> -    id = i2c_of_match_device(dev->driver->of_match_table, client);
> -    if (id)
> -        priv->type = (uintptr_t)id->data;
> +    priv->type = (uintptr_t)device_get_match_data(dev);
> +
>      i2c_set_clientdata(client, priv);
> 
>      err = ht16k33_initialize(priv);
> 
> Or do you think falling back to DISP_MATRIX if no match is found is wrong?

First of all, the I²C ID table should actually use DISP_MATRIX.

Second, there are two points:

- It would be nice to check if the OF ID table doesn't provide a setting
  (shouldn't we try I²C ID table and then, if still nothing, bail out?)

- The I²C ID table can be extended in the future with another entry which
  may want to have different default


-- 
With Best Regards,
Andy Shevchenko