Re: [PATCH RFC 3/4] gpio: loongson-64bit: Add shared interrupt support

[Miao Wang <shankerwangmiao@gmail.com>]

Hi, 

> 2026年10月1日 16:59，Miao Wang <shankerwangmiao@gmail.com> 写道：
> 
> Hi Linus,
> 
> Thanks for your suggestions.
> 
>> 2026年10月01日 16:33，Linus Walleij <linusw@kernel.org> 写道：
>> 
>> Hi Miao,
>> 
>> thanks for your patch!
>> 
>> On Fri, Sep 25, 2026 at 6:28 PM Miao Wang via B4 Relay
>> <devnull+shankerwangmiao.gmail.com@kernel.org> wrote:
>> 
>>> +struct loongson_gpio_shared_per_parent_irq_data {
>>> +       unsigned int parent_index;
>>> +       unsigned int parent_irq;
>>> +       /*
>>> +        * The lock of the irq_desc of the parent irq also protects
>>> +        * exclusive/usedby below. It must be taken before
>>> +        * lgpio->shared_irq_data->lock.
>>> +        */
>>> +       struct irq_data *parent_irq_data;
>>> +       struct loongson_gpio_chip *lgpio;
>>> +
>>> +       /*
>>> +        * exclusive: exclusive usage, only one gpio pin can use this parent irq.
>>> +        *   It will happen in two cases:
>>> +        *     - The parent irq is used by a gpio pin which is edge triggered, and
>>> +        *       thus cannot be used by other gpio pins which are mapped to the same
>>> +        *       parent irq.
>>> +        *     - The parent irq is used by a gpio pin which is level triggered, and
>>> +        *       the gpio chip lacks the polarity control register, and thus the
>>> +        *       interrupt polarity is controlled by the parent irq controller, and
>>> +        *       thus cannot be used by other gpio pins which are mapped to the
>>> +        *       same parent irq.
>>> +        *   When set, the request for other gpio pins which are mapped to this
>>> +        *   parent irq will be rejected.
>>> +        */
>>> +       unsigned int exclusive : 1;
>> 
>> So use bool exclusive;
>> 
>>> +       /*
>>> +        * usedby: When exclusive is set, these bits indicate the gpio pin which
>>> +        *   is using this parent irq. When exclusive is cleared, these bits
>>> +        *   indicate the number of gpio pins which are using this parent irq.
>>> +        * When both exclusive and usedby are 0, it means that the parent irq is not
>>> +        * used by any gpio pin.
>>> +        */
>>> +       unsigned int usedby : 31;
>> 
>> Is this a bitmap? Then use a bitmap abstraction.
> 
> When exclusive is 1, it is a pure number while when exclusive is 0, 
> it is a bitmap.

To correct my self, usedby is not a bitmap. When exclusive is 1, it stores the using pin
id, while when exclusive is zero, it is a counter which stores the number of using pins.

Cheers,

Miao Wang