Re: [RFC PATCH v2 5/7] of: hw_prober: Support Chromebook SKU ID based component selection

From: Rob Herring <robh@kernel.org>
To: Chen-Yu Tsai <wenst@chromium.org>
Cc: Frank Rowand <frowand.list@gmail.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno 
	<angelogioacchino.delregno@collabora.com>,
	Hsin-Yi Wang <hsinyi@chromium.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	andriy.shevchenko@linux.intel.com, Jiri Kosina <jikos@kernel.org>,
	linus.walleij@linaro.org, broonie@kernel.org,
	gregkh@linuxfoundation.org, hdegoede@redhat.com,
	james.clark@arm.com, james@equiv.tech, keescook@chromium.org,
	petr.tesarik.ext@huawei.com, rafael@kernel.org,
	tglx@linutronix.de, Jeff LaBundy <jeff@labundy.com>,
	linux-input@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
	Douglas Anderson <dianders@chromium.org>,
	Johan Hovold <johan@kernel.org>
Subject: Re: [RFC PATCH v2 5/7] of: hw_prober: Support Chromebook SKU ID based component selection
Date: Fri, 10 Nov 2023 15:07:16 -0600	[thread overview]
Message-ID: <20231110210716.GB419831-robh@kernel.org> (raw)
In-Reply-To: <20231109100606.1245545-6-wenst@chromium.org>

On Thu, Nov 09, 2023 at 06:06:02PM +0800, Chen-Yu Tsai wrote:
> In cases where the same Chromebook model is manufactured with different
> components (MIPI DSI panels, MIPI CSI camera sensors, or trackpad /
> touchscreens with conflicting addresses), a different SKU ID is
> allocated to each specific combination. This SKU ID is exported by the
> bootloader into the device tree, and can be used to "discover" which
> combination is present on the current machine.
> 
> This change adds a hardware prober that will match the SKU ID against
> a provided table, and enable the component for the matched entry based
> on the given compatible string. In the MIPI DSI panel and MIPI CSI
> camera sensor cases which have OF graphs, it will also update the
> remote endpoint to point to the enabled component. This assumes a single
> endpoint only.
> 
> This will provide a path to reducing the number of Chromebook device
> trees.
> 
> Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> ---
>  drivers/of/hw_prober.c | 160 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 160 insertions(+)

This certainly does not belong in drivers/of/.

> diff --git a/drivers/of/hw_prober.c b/drivers/of/hw_prober.c
> index 442da6eff896..4345e5aed6d8 100644
> --- a/drivers/of/hw_prober.c
> +++ b/drivers/of/hw_prober.c
> @@ -8,6 +8,7 @@
>  #include <linux/array_size.h>
>  #include <linux/i2c.h>
>  #include <linux/of.h>
> +#include <linux/of_graph.h>
>  #include <linux/platform_device.h>
>  
>  #define DRV_NAME	"hw_prober"
> @@ -108,9 +109,168 @@ static int i2c_component_prober(struct platform_device *pdev, const void *data)
>  	return ret;
>  }
>  
> +static int cros_get_coreboot_sku_id(struct device *dev, u32 *sku_id)
> +{
> +	struct device_node *node = NULL;
> +	int ret;
> +
> +	node = of_find_node_by_path("/firmware/coreboot");
> +	if (!node)
> +		return dev_err_probe(dev, -EINVAL, "Cannot find coreboot firmware node\n");
> +
> +	ret = of_property_read_u32(node, "sku-id", sku_id);

Not documented.

Rob