[PATCH 0/1] nvme: Export CSTS register via sysfs

[Alan Adamson]

> On Mar 18, 2021, at 9:52 AM, Keith Busch <kbusch at kernel.org> wrote:
> 
> On Thu, Mar 18, 2021 at 04:28:24PM +0000, Alan Adamson wrote:
>> 
>> 
>>> On Mar 17, 2021, at 9:38 PM, Christoph Hellwig <hch at lst.de> wrote:
>>> 
>>> On Wed, Mar 17, 2021 at 04:46:14PM -0400, Alan Adamson wrote:
>>>> This patch exports the NVMe Controller CSTS register via sysfs.  This
>>>> feature can be used by userland executables that accessed CSTS and
>>>> possibly other registers by mapping them into user space.  Since this ability
>>>> may not always available, exporting certain registers via sysfs provides
>>>> a safe/read-only way to access registers from outside the kernel.
>>> 
>>> So what is this application doings with it?  Should we just have a
>>> ready attribute instead of exporting a raw register encoding?
>> 
>> 
>> Was using nvme-cli show-regs to manage nvme devices. This is no longer an option.
> 
> Most distributions ship with kernel CONFIG_IO_STRICT_DEVMEM these days,
> so that user command will very rarely work on PCIe targets anymore.
> 
> Perhaps we could introduce a driver option allowing read-only mmap on
> this memory?  While you're currently asking for just one register
> attribute, it would be nice if we can make all future requests available
> without piling on more sysfs properties.

This could be a good solution (along with a nvme-cli change).  I’ll code this up.

Thanks,

Alan