linux-kernel - Re: [RFC v2 PATCH 03/14] irq: add new struct ipi

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Message-ID: <561D148E.9020208@imgtec.com>
Date:	Tue, 13 Oct 2015 15:26:22 +0100
From:	Qais Yousef <qais.yousef@...tec.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	<linux-kernel@...r.kernel.org>, <jason@...edaemon.net>,
	<marc.zyngier@....com>, <jiang.liu@...ux.intel.com>,
	<ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>
Subject: Re: [RFC v2 PATCH 03/14] irq: add new struct ipi_mask

On 10/13/2015 02:26 PM, Thomas Gleixner wrote:
> On Tue, 13 Oct 2015, Qais Yousef wrote:
>> cpumask is limited to NR_CPUS. introduce ipi_mask which allows us to address
>> cpu range that is higher than NR_CPUS which is required for drivers to send
>> IPIs for coprocessor that are outside Linux CPU range.
>>
>> Signed-off-by: Qais Yousef <qais.yousef@...tec.com>
>> ---
>>   include/linux/irq.h | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/include/linux/irq.h b/include/linux/irq.h
>> index 11bf09288ddb..4b537e4d393b 100644
>> --- a/include/linux/irq.h
>> +++ b/include/linux/irq.h
>> @@ -125,6 +125,21 @@ enum {
>>   struct msi_desc;
>>   struct irq_domain;
>>   
>> + /**
>> + * struct ipi_mask - IPI mask information
>> + * @cpumask: bitmap of cpumasks
>> + * @nbits: number of bits in cpumask
>> + * @global: whether the mask is SMP IPI ie: subset of cpu_possible_mask or not
>> + *
>> + * ipi_mask is similar to cpumask, but it provides nbits that's configurable
>> + * rather than fixed to NR_CPUS.
>> + */
>> +struct ipi_mask {
>> +	unsigned long	*cpumask;
>> +	unsigned int	nbits;
>> +	bool		global;
>> +};
> Can you make that:
>
> struct ipi_mask {
> 	unsigned int	nbits;
> 	bool		global;
> 	unsigned long	cpu_bitmap[];
> };
>
> That allows you to allocate the data structure in one go. So the
> ipi_mask in irq_data_common becomes a pointer which is only filled in
> when ipi_mask is actually used.
>
> Note, I renamed cpumask to cpu_bitmap to avoid confusion with
> cpumasks.
>
> We also want a helper function
>
>     struct cpumask *irq_data_get_ipi_mask(struct irq_data *data);
>
> so we can use normal cpumask operations for the majority of cases.
>
>

Will do.

Thanks,
Qais
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