linux-kernel - Re: [PATCH] nvme: Fix nvme_get/set_features() with a NULL result pointer

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Date:   Thu, 25 Aug 2016 08:20:27 -0600
From:   Jens Axboe <axboe@...com>
To:     Andy Lutomirski <luto@...capital.net>,
        Christoph Hellwig <hch@....de>
CC:     Andy Lutomirski <luto@...nel.org>,
        Keith Busch <keith.busch@...el.com>,
        <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] nvme: Fix nvme_get/set_features() with a NULL result
 pointer

On 08/25/2016 01:54 AM, Andy Lutomirski wrote:
> On Thu, Aug 25, 2016 at 12:38 AM, Christoph Hellwig <hch@....de> wrote:
>> Ooops, yes.
>>
>> Are you looking into new nvme_set_features users?  Another thing
>> we need to tackle is either replacing dma_addr argument with a
>> a real kernel pointer (or just kill it until users show up)
>
> I am, and I have a patch to do the former (and to add a length
> argument).  But that's not -stable material.
>
> While I have your attention: the new use is to enable APST (power
> saving).  In theory, it seems like I should integrate with dev_pm_qos
> so that the standard interface for setting a latency limit will work,
> but, on brief inspection, there are literally no drivers in the entire
> tree that do this.  Am I missing something?  My current draft patch
> just adds a sysfs attribute.  (It saves a *lot* of power on my laptop,
> so supporting APST is worth doing.)

Care to send out what you have? I'd be interested in seeing how much I
can save on my laptop, haven't played with APST yet.

-- 
Jens Axboe