linux-kernel - Re: [PATCH] mmc: block: Add new ioctl to send multi commands

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Message-ID: <CANEJEGuPm_PdBb39iCOdCcSKVMUi3jpiPb_Jgp951xyJvp_3rg@mail.gmail.com>
Date:	Thu, 10 Sep 2015 13:26:20 -0700
From:	Grant Grundler <grundler@...gle.com>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Olof Johansson <olofj@...omium.org>,
	Seshagiri Holi <sholi@...dia.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: block: Add new ioctl to send multi commands

On Thu, Sep 10, 2015 at 11:20 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>
> On 10/09/15 18:10, Grant Grundler wrote:
...
>>>>>> struct mmc_ioc_multi_cmd {
>>>>>>     __u64 num_of_cmds;
>>>>>>     struct mmc_ioc_cmd cmds[0];
>>>>>> };
>>
>> I think this would work just as well. But doesn't "pointer to an
>> array" require 32-bit ioctl compat handling?
>> We were trying to avoid a 32-bit user space compatibility handler.
>
> I think that this is fine as it is a zero length array [0] and not a
> pointer.

Doh, yes. Thanks for correcting. I knew this was a gcc special but
forgot it's not actually allocating any space.

cheers,
grant

>
> Cheers
> Jon
>
> [0] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
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