[ipxe-devel] [PATCH 1/4] [pci] Add pci_find_next_capability

[Michael S. Tsirkin]

On Wed, Mar 09, 2016 at 07:20:00PM +0100, Ladi Prosek wrote:
> PCI devices may support more capabilities of the same type (for
> example PCI_CAP_ID_VNDR) and there was no way to discover all of
> them. This commit adds a new API pci_find_next_capability which
> provides this functionality. It would typically be used like so:
> 
>   for (pos = pci_find_capability(pci, PCI_CAP_ID_VNDR);
>        pos > 0;
>        pos = pci_find_next_capability(pci, pos, PCI_CAP_ID_VNDR)) {
>     ...
>   }
> 
> Signed-off-by: Ladi Prosek <lprosek at redhat.com>


Reviewed-by: Michael S. Tsirkin <mst at redhat.com>

> ---
>  src/drivers/bus/pciextra.c | 54 +++++++++++++++++++++++++++++++++++-----------
>  src/include/ipxe/pci.h     |  2 ++
>  2 files changed, 43 insertions(+), 13 deletions(-)
> 
> diff --git a/src/drivers/bus/pciextra.c b/src/drivers/bus/pciextra.c
> index 82287fb..15f79c9 100644
> --- a/src/drivers/bus/pciextra.c
> +++ b/src/drivers/bus/pciextra.c
> @@ -3,6 +3,24 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
>  #include <stdint.h>
>  #include <ipxe/pci.h>
>  
> +static int pci_find_capability_common ( struct pci_device *pci,
> +		   uint8_t pos, int cap ) {
> +	uint8_t id;
> +	int ttl = 48;
> +
> +	while ( ttl-- && pos >= 0x40
> ) {
> +		pos &= ~3;
> +		pci_read_config_byte ( pci, pos + PCI_CAP_ID, &id );
> +		DBG ( "PCI Capability: %d\n", id );
> +		if ( id == 0xff )
> +			break;
> +		if ( id == cap )
> +			return pos;
> +		pci_read_config_byte ( pci, pos + PCI_CAP_NEXT, &pos );
> +	}
> +	return 0;
> +}
> +
>  /**
>   * Look for a PCI capability
>   *
> @@ -17,9 +35,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
>   */
>  int pci_find_capability ( struct pci_device *pci, int cap ) {
>  	uint16_t status;
> -	uint8_t pos, id;
> +	uint8_t pos;
>  	uint8_t hdr_type;
> -	int ttl = 48;
>  
>  	pci_read_config_word ( pci, PCI_STATUS, &status );
>  	if ( ! ( status & PCI_STATUS_CAP_LIST ) )
> @@ -36,17 +53,28 @@ int pci_find_capability ( struct pci_device *pci, int cap ) {
>  		pci_read_config_byte ( pci, PCI_CB_CAPABILITY_LIST, &pos );
>  		break;
>  	}
> -	while ( ttl-- && pos >= 0x40 ) {
> -		pos &= ~3;
> -		pci_read_config_byte ( pci, pos + PCI_CAP_ID, &id );
> -		DBG ( "PCI Capability: %d\n", id );
> -		if ( id == 0xff )
> -			break;
> -		if ( id == cap )
> -			return pos;
> -		pci_read_config_byte ( pci, pos + PCI_CAP_NEXT, &pos );
> -	}
> -	return 0;
> +	return pci_find_capability_common ( pci, pos, cap );
> +}
> +
> +/**
> + * Look for another PCI capability
> + *
> + * @v pci		PCI device to query
> + * @v pos		Address of the current capability
> + * @v cap		Capability code
> + * @ret address		Address of capability, or 0 if not found
> + *
> + * Determine whether or not a device supports a given PCI capability
> + * starting the search at a given address within the device's PCI
> + * configuration space. Returns the address of the next capability
> + * structure within the device's PCI configuration space, or 0 if the
> + * device does not support another such capability.
> + */
> +int pci_find_next_capability ( struct pci_device *pci, int pos, int cap ) {
> +	u8 new_pos;
> +
> +	pci_read_config_byte ( pci, pos + PCI_CAP_NEXT, &new_pos );
> +	return pci_find_capability_common ( pci, new_pos, cap );
>  }
>  
>  /**
> diff --git a/src/include/ipxe/pci.h b/src/include/ipxe/pci.h
> index 89d9d80..0c6bc7e 100644
> --- a/src/include/ipxe/pci.h
> +++ b/src/include/ipxe/pci.h
> @@ -286,6 +286,8 @@ extern int pci_find_driver ( struct pci_device *pci );
>  extern int pci_probe ( struct pci_device *pci );
>  extern void pci_remove ( struct pci_device *pci );
>  extern int pci_find_capability ( struct pci_device *pci, int capability );
> +extern int pci_find_next_capability ( struct pci_device *pci,
> +				      int pos, int capability );
>  extern unsigned long pci_bar_size ( struct pci_device *pci, unsigned int reg );
>  
>  /**
> -- 
> 2.5.0