linux-kernel - Re: [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs

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Date:   Tue, 15 Sep 2020 11:51:02 +0200
From:   Arnaud POULIQUEN <arnaud.pouliquen@...com>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>,
        "tsoni@...eaurora.org" <tsoni@...eaurora.org>,
        "psodagud@...eaurora.org" <psodagud@...eaurora.org>,
        "sidgup@...eaurora.org" <sidgup@...eaurora.org>
Subject: Re: [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs

Hi Rishabh,

On 8/27/20 9:48 PM, Rishabh Bhatnagar wrote:
> From Android R onwards Google has restricted access to debugfs in user
> and user-debug builds. This restricts access to most of the features
> exposed through debugfs. This patch series adds a configurable option
> to move the recovery/coredump interfaces to sysfs. If the feature
> flag is selected it would move these interfaces to sysfs and remove
> the equivalent debugfs interface. 'Coredump' and 'Recovery' are critical
> interfaces that are required for remoteproc to work on Qualcomm Chipsets.
> Coredump configuration needs to be set to "inline" in debug/test build
> and "disabled" in production builds. Whereas recovery needs to be
> "disabled" for debugging purposes and "enabled" on production builds.

The remoteproc_cdev had been created to respond to some sysfs limitations.
I wonder if this evolution should not also be implemented in the cdev.
In this case an additional event could be addedd to inform the application
that a crash occurred and that a core dump is available.

Of course it's only a suggestion... As it would be a redesign.
I let Björn and Mathieu comment.

Regards,
Arnaud

> 
> Changelog:
> 
> v1 -> v2:
> - Correct the contact name in the sysfs documentation.
> - Remove the redundant write documentation for coredump/recovery sysfs
> - Add a feature flag to make this interface switch configurable.
> 
> Rishabh Bhatnagar (3):
>   remoteproc: Expose remoteproc configuration through sysfs
>   remoteproc: Add coredump configuration to sysfs
>   remoteproc: Add recovery configuration to sysfs
> 
>  Documentation/ABI/testing/sysfs-class-remoteproc |  44 ++++++++
>  drivers/remoteproc/Kconfig                       |  12 +++
>  drivers/remoteproc/remoteproc_debugfs.c          |  10 +-
>  drivers/remoteproc/remoteproc_sysfs.c            | 126 +++++++++++++++++++++++
>  4 files changed, 190 insertions(+), 2 deletions(-)
>