linux-kernel - Re: [PATCH v2 02/11] PCI: Add the pci_get_class

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Date:   Thu, 10 Aug 2023 21:05:44 +0800
From:   suijingfeng <suijingfeng@...ngson.cn>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Dave Airlie <airlied@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>, linux-pci@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/11] PCI: Add the pci_get_class_masked() helper

Hi,


On 2023/8/9 22:01, Ilpo Järvinen wrote:
> On Wed, 9 Aug 2023, Sui Jingfeng wrote:
>
>> From: Sui Jingfeng <suijingfeng@...ngson.cn>
>>
>> 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@...ngson.cn>
>> ---
>>   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; }
>>