Re: [PATCH v2 02/11] PCI: Add the pci_get_class_masked() helper

[suijingfeng]

Hi,


On 2023/8/9 22:01, Ilpo Järvinen wrote:
> On Wed, 9 Aug 2023, Sui Jingfeng wrote:
>
> > From: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> >
> > Because there is no good way to get the mask member used to searching for
> > devices that conform to a specific PCI class code, an application needs to
> > process all PCI display devices can achieve its goal as follows:
> This is mixing old and new way in a single sentence (which is confusing)?


Thanks for reviewing, but I can't understand this sentence.
Are you telling me that my description have grammar problem or something else?


I means that before apply this patch, we don't have a function can be used
to get all PCI(e) devices in a system by matching against its the PCI base class code only,
while keep the Sub-Class code and the Programming Interface ignored.
By supply a mask as argument, such thing become possible.

If an application want to process all PCI display devices in the system,
then it can achieve its goal by calling pci_get_class_masked() function.


> > pdev = NULL;
> > do {
> > 	pdev = pci_get_class_masked(PCI_BASE_CLASS_DISPLAY << 16, 0xFF0000, pdev);
> > 	if (pdev)
> > 		do_something_for_pci_display_device(pdev);
> > } while (pdev);
> >
> > While previously, we just can not ignore Sub-Class code and the Programming
> cannot
>
> > Interface byte when do the searching.
> doing the search.


OK, will be fixed at the next version.


> > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > ---
> >   drivers/pci/search.c | 30 ++++++++++++++++++++++++++++++
> >   include/linux/pci.h  |  7 +++++++
> >   2 files changed, 37 insertions(+)
> >
> > diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> > index b4c138a6ec02..f1c15aea868b 100644
> > --- a/drivers/pci/search.c
> > +++ b/drivers/pci/search.c
> > @@ -334,6 +334,36 @@ struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
> >   }
> >   EXPORT_SYMBOL(pci_get_device);
> >   
> > +/**
> > + * pci_get_class_masked - begin or continue searching for a PCI device by class and mask
> > + * @class: search for a PCI device with this class designation
> > + * @from: Previous PCI device found in search, or %NULL for new search.
> > + *
> > + * Iterates through the list of known PCI devices.  If a PCI device is
> No double spaces in kernel comments. Perhaps your editor might be adding
> them on reflow (might be configurable to not do that).
>
> > + * found with a matching @class, the reference count to the device is
> > + * incremented and a pointer to its device structure is returned.
> > + * Otherwise, %NULL is returned.
> > + * A new search is initiated by passing %NULL as the @from argument.
> > + * Otherwise if @from is not %NULL, searches continue from next device
> > + * on the global list.  The reference count for @from is always decremented
> > + * if it is not %NULL.
> Use kerneldoc's Return: section for describing return value.
>
> > + */
> > +struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
> > +				     struct pci_dev *from)
> > +{
> > +	struct pci_device_id id = {
> > +		.vendor = PCI_ANY_ID,
> > +		.device = PCI_ANY_ID,
> > +		.subvendor = PCI_ANY_ID,
> > +		.subdevice = PCI_ANY_ID,
> > +		.class_mask = mask,
> > +		.class = class,
> > +	};
> > +
> > +	return pci_get_dev_by_id(&id, from);
> > +}
> > +EXPORT_SYMBOL(pci_get_class_masked);
> > +
> >   /**
> >    * pci_get_class - begin or continue searching for a PCI device by class
> >    * @class: search for a PCI device with this class designation
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 0ff7500772e6..b20e7ba844bf 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1180,6 +1180,9 @@ struct pci_dev *pci_get_slot(struct pci_bus *bus, unsigned int devfn);
> >   struct pci_dev *pci_get_domain_bus_and_slot(int domain, unsigned int bus,
> >   					    unsigned int devfn);
> >   struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from);
> > +struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
> > +				     struct pci_dev *from);
> > +
> >   int pci_dev_present(const struct pci_device_id *ids);
> >   
> >   int pci_bus_read_config_byte(struct pci_bus *bus, unsigned int devfn,
> > @@ -1895,6 +1898,10 @@ static inline struct pci_dev *pci_get_class(unsigned int class,
> >   					    struct pci_dev *from)
> >   { return NULL; }
> >   
> > +static inline struct pci_dev *pci_get_class_masked(unsigned int class,
> > +						   unsigned int mask,
> > +						   struct pci_dev *from)
> > +{ return NULL; }
> >   
> >   static inline int pci_dev_present(const struct pci_device_id *ids)
> >   { return 0; }