linux-kernel - RE: [PATCH 0/5] Add uv

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Date:   Wed, 18 Nov 2020 16:07:56 +0000
From:   "Ernst, Justin" <justin.ernst@....com>
To:     Hans de Goede <hdegoede@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "Ingo Molnar" <mingo@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Wahl, Steve" <steve.wahl@....com>,
        "x86@...nel.org" <x86@...nel.org>
CC:     Andy Shevchenko <andy@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        "Sivanich, Dimitri" <dimitri.sivanich@....com>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Anderson, Russ" <russ.anderson@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Ilya Dryomov <idryomov@...il.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Mauro Carvalho Chehab" <mchehab+huawei@...nel.org>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>
Subject: RE: [PATCH 0/5] Add uv_sysfs platform driver

> Hi,
> 
> On 11/17/20 9:42 PM, Justin Ernst wrote:
> > Introduce a new platform driver to gather topology information from UV systems
> > and expose that information via a sysfs interface at /sys/firmware/sgi_uv/.
> >
> > Justin Ernst (5):
> >   x86/platform/uv: Remove existing /sys/firmware/sgi_uv/ interface
> >   x86/platform/uv: Add and export uv_bios_* functions
> >   x86/platform/uv: Add new uv_sysfs platform driver
> >   x86/platform/uv: Update ABI documentation of /sys/firmware/sgi_uv/
> >   x86/platform/uv: Update MAINTAINERS for uv_sysfs driver
> 
> So patch 1/1 drops the existing
> 
> /sys/firmware/sgi_uv/coherence_id
> /sys/firmware/sgi_uv/partition_id
> 
> sysfs API, then according to patch 4/5 patch 3/5 reintroduces
> the /sys/firmware/sgi_uv/partition_id API, but the /sys/firmware/sgi_uv/coherence_id
> file is gone for ever ?
> 
> I'm not sure what userspace bits (may) depend on this but without more info
> this looks like a clear violation of the do not break userspace APIs rule.
> 
> So, based on this, I have to nack this series in its current state.
> 
> Now if there is a strong believe there are 0 (not a few, but _zero_) users
> out there who rely on the /sys/firmware/sgi_uv/coherence_id file then this
> might be ok. But then there needs to be a technical analysis of why this is
> ok in the commit message of the patch dropping this sysfs file.
> 
> Also the commit message of patch 1/5 should mention that
> /sys/firmware/sgi_uv/partition_id will be re-introduced later through
> another driver.

Hello Hans,

I will resubmit these patches without the API breakage, reintroducing the coherence_id file in the new driver.

Thank you for taking the time to look over my patch set.

> 
> Regards,
> 
> Hans