Re: [PATCH v3] mailbox: test: really ignore optional memory resources

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

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On Tue, Mar 03, 2026 at 10:27:39PM +0100, Wolfram Sang wrote:
> Memory resources are optional but if the resource is empty
> devm_platform_get_and_ioremap_resource() prints an error nonetheless.
> Refactor the code to check the resources locally first and process them
> only if they are present. The -EBUSY error message of ioremap_resource()
> is still kept because it is correct. The comment which explains that a
> plain ioremap() is tried as a workaround is turned into a info message.
> So, a user will be informed about it, too.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---

Changes since v2:

* refactored mbox_test_ioremap() to have multiple exits which makes the
  logic easier to understand IMHO (Thanks, Geert, for the suggestions!)


>  drivers/mailbox/mailbox-test.c | 37 +++++++++++++++++++---------------
>  1 file changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
> index cfd5429df17e..df53d918d9fa 100644
> --- a/drivers/mailbox/mailbox-test.c
> +++ b/drivers/mailbox/mailbox-test.c
> @@ -356,11 +356,27 @@ mbox_test_request_channel(struct platform_device *pdev, const char *name)
>  	return channel;
>  }
>  
> +static void *mbox_test_ioremap(struct platform_device *pdev, unsigned int res_num)
> +{
> +	struct resource *res;
> +	void *mmio;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, res_num);
> +	if (!res)
> +		return NULL;
> +
> +	mmio = devm_ioremap_resource(&pdev->dev, res);
> +	if (PTR_ERR(mmio) == -EBUSY) {
> +		dev_info(&pdev->dev, "trying workaround with plain ioremap\n");
> +		return devm_ioremap(&pdev->dev, res->start, resource_size(res));
> +	}
> +
> +	return IS_ERR(mmio) ? NULL : mmio;
> +}
> +
>  static int mbox_test_probe(struct platform_device *pdev)
>  {
>  	struct mbox_test_device *tdev;
> -	struct resource *res;
> -	resource_size_t size;
>  	int ret;
>  
>  	tdev = devm_kzalloc(&pdev->dev, sizeof(*tdev), GFP_KERNEL);
> @@ -368,23 +384,12 @@ static int mbox_test_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	/* It's okay for MMIO to be NULL */
> -	tdev->tx_mmio = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> -	if (PTR_ERR(tdev->tx_mmio) == -EBUSY) {
> -		/* if reserved area in SRAM, try just ioremap */
> -		size = resource_size(res);
> -		tdev->tx_mmio = devm_ioremap(&pdev->dev, res->start, size);
> -	} else if (IS_ERR(tdev->tx_mmio)) {
> -		tdev->tx_mmio = NULL;
> -	}
> +	tdev->tx_mmio = mbox_test_ioremap(pdev, 0);
>  
>  	/* If specified, second reg entry is Rx MMIO */
> -	tdev->rx_mmio = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
> -	if (PTR_ERR(tdev->rx_mmio) == -EBUSY) {
> -		size = resource_size(res);
> -		tdev->rx_mmio = devm_ioremap(&pdev->dev, res->start, size);
> -	} else if (IS_ERR(tdev->rx_mmio)) {
> +	tdev->rx_mmio = mbox_test_ioremap(pdev, 1);
> +	if (!tdev->rx_mmio)
>  		tdev->rx_mmio = tdev->tx_mmio;
> -	}
>  
>  	tdev->tx_channel = mbox_test_request_channel(pdev, "tx");
>  	tdev->rx_channel = mbox_test_request_channel(pdev, "rx");
> -- 
> 2.51.0
> 

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