Re: [PATCH 09/15] cxl/acpi: Determine PCI host bridge's ACPI UID

[Jonathan Zhang (Infra)]

> On Aug 31, 2022, at 1:15 AM, Robert Richter <rrichter@xxxxxxx> wrote:
> 
> The UID is needed to read the RCH's CEDT entry with the RCRB base
> address. Determine the host's UID from its ACPI fw node.
> 
> Signed-off-by: Robert Richter <rrichter@xxxxxxx>
> ---
> drivers/cxl/acpi.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index f9cdf23a91a8..b3146b7ae922 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -368,8 +368,20 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
> static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> {
> 	struct pci_host_bridge *host = NULL;
> +	struct acpi_device *adev;
> +	unsigned long long uid = ~0;
> 
> 	while ((host = cxl_find_next_rch(host)) != NULL) {
> +		adev = ACPI_COMPANION(&host->dev);
> +		if (!adev || !adev->pnp.unique_id ||
> +			(kstrtoull(adev->pnp.unique_id, 10, &uid) < 0))
The UID field holds 4 bytes of ASCII characters. kstrtoull() would fail
if the UID field has value such as ‘CX03’.

> +			continue;
> +
> +		dev_dbg(&adev->dev, "host uid: %llu\n", uid);
> +
> +		if (uid > U32_MAX)
> +			continue;
> +
> 		dev_info(&host->dev, "host supports CXL\n");
> 	}
> 
> -- 
> 2.30.2
> 
>