Re: [PATCH v6 10/31] xen/arm: ITS: Introduce gic_is_lpi helper function

[Julien Grall <julien.grall@citrix.com>]

Hi,

On 03/09/2015 07:32, Vijay Kilari wrote:
> On Tue, Sep 1, 2015 at 6:32 PM, Julien Grall <julien.grall@citrix.com> wrote:
>> On 01/09/15 12:56, Vijay Kilari wrote:
>>>> BTW, I suggested to create a field nr_lpis but you decided to store the
>>>> number of bits supported. Why?
>>>
>>> I have nr_lpis field in vgic structure (patch #17). But it just tells
>>> how LPIs are supported
>>> for a domain.
>>
>> Why are you speaking about vgic structure? I'm only suggesting to
>> replace you nr_id_bits by nr_lpis in the hw GIC. AFAICT, there is
>> nothing to prevent having 2 field using the same name on 2 differents
>> structure...
>>
>>> Where as nr_id_bits shows total number of  lpis that hw supports.
>>
>> No nr_id_bits shows the total number of interrupt not LPIs. The total
>> number of LPIs is (1 << nr_id_bits) - 8092. Although (1 << nr_id_bits)
>> gives you the last LPI interrupt ID supported.
>>
>> Anyway, as I said earlier, re-calculating the last LPI interrupt ID
>> everytime based on the shift is time consuming. You should optimize for
>> the common case rather than using copy the raw value (i.e ID bits) from
>> the HW directly.
>>
>> Maybe the name "max_lpi_id" would make more sense to you for a name?
>
> Instead of storing max_lpi_id which is ( 1 << nr_id_bits) - 8192, I prefer
> to rename nr_id_bits as nr_irq_ids which can be initialized to (1 << nr_id_bits)
> for gicv3 and gicv2_info.nr_lines for gicv2.

I'm fine with that.

Regards,

-- 
Julien Grall