Re: [PATCH 1/2] mei: me: Add exported function to check ME device availabiliy

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Jul 15, 2025 at 04:00:01PM -0700, Daniele Ceraolo Spurio wrote:
> The intel GFX drivers (i915/xe) interface with the ME device for some of
> their features (e.g. PXP, HDCP) via the component interface. Given that
> the MEI device can be hidden by BIOS/Coreboot, the GFX drivers need a
> way to check if the device is available before attempting to bind the
> component, otherwise they'll go ahead and initialize features that will
> never work.
> The simplest way to check if the device is available is to check the
> available devices against the PCI ID list of the mei_me driver. To avoid
> duplication of the list, the function to do such a check is added to
> the mei_me driver and exported so that the GFX driver can call it
> directly.
> 
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Alexander Usyskin <alexander.usyskin@intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  drivers/misc/mei/pci-me.c | 17 +++++++++++++++++
>  include/linux/mei_me.h    | 20 ++++++++++++++++++++
>  2 files changed, 37 insertions(+)
>  create mode 100644 include/linux/mei_me.h
> 
> diff --git a/drivers/misc/mei/pci-me.c b/drivers/misc/mei/pci-me.c
> index 3f9c60b579ae..16e9a11eb286 100644
> --- a/drivers/misc/mei/pci-me.c
> +++ b/drivers/misc/mei/pci-me.c
> @@ -18,6 +18,7 @@
>  #include <linux/pm_runtime.h>
>  
>  #include <linux/mei.h>
> +#include <linux/mei_me.h>
>  
>  #include "mei_dev.h"
>  #include "client.h"
> @@ -133,6 +134,22 @@ static const struct pci_device_id mei_me_pci_tbl[] = {
>  
>  MODULE_DEVICE_TABLE(pci, mei_me_pci_tbl);
>  
> +/**
> + * mei_me_device_present - check if an ME device is present on the system
> + *
> + * Other drivers (e.g., i915, xe) interface with the ME device for some of their
> + * features (e.g., PXP, HDCP). However, the ME device can be hidden by
> + * BIOS/coreboot, so this function offers a way for those drivers to check if
> + * the device is available before attempting to interface with it.
> + *
> + * Return: true if an ME device is available, false otherwise
> + */
> +bool mei_me_device_present(void)
> +{
> +	return pci_dev_present(mei_me_pci_tbl);

And what happens if the device goes away right after you call this?

> +}
> +EXPORT_SYMBOL(mei_me_device_present);

EXPORT_SYMBOL_GPL()?  I have to ask, sorry.

And where is patch 2/2?

thanks,

greg k-h