linux-kernel - Re: [PATCH v1] mei: Don't encourage to use kernel internal types in user code

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Message-ID: <20200302155818.GG1224808@smile.fi.intel.com>
Date:   Mon, 2 Mar 2020 17:58:18 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v1] mei: Don't encourage to use kernel internal types in
 user code

+Cc: Christoph.

On Sat, Feb 29, 2020 at 04:28:11PM +0000, Winkler, Tomas wrote:
> > uuid_le is internal kernel type which shall not be exposed to the user in the first
> > place. 
> Why, these types are exported via include/uapi/linux/uuid.h

Which is wrong from the day 1.

The uuid_t type is being provided by libuuid in the user space, there is no
(more) kernel exported equivalent. Same should be done to the uuid_le.

We already discussed this couple of years ago.

> In order to mitigate the (wrong) distribution of the use of that type,
> > switch MEI AMT sample to plain unsigned char array.
> 
> There was a change to guid_t from uuild_le, anyhow there is much more code
>  except this sample that uses those types. 

I guess you misunderstood the point. The types are for kernel use and keeping them
exported in a condition like it's now (quoter baked due to drop of uuid_be part
completely and uuid_le partially) is wrong.

There is *no* ABI change. And basically libuuid or another one should provide
type and infrastructure for this.

> Nack so far.

If you would like to bear the legacy type, why not to move this UUID UAPI parts
directly to MEI?

-- 
With Best Regards,
Andy Shevchenko