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

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Date:   Thu, 3 Sep 2020 13:45:19 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     rishabhb@...eaurora.org
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, tsoni@...eaurora.org,
        psodagud@...eaurora.org, sidgup@...eaurora.org,
        linux-remoteproc-owner@...r.kernel.org
Subject: Re: [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs

On Wed, Sep 02, 2020 at 04:14:19PM -0700, rishabhb@...eaurora.org wrote:
> On 2020-09-01 15:05, Mathieu Poirier wrote:
> > Hi Rishabh,
> > 
> > On Thu, Aug 27, 2020 at 12:48:48PM -0700, 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.
> > 
> > What I meant wast to move the coredump entry from debugfs to sysfs and
> > from
> > there make it available to user space using a kernel config.  But
> > thinking
> > further on this it may be better to simply provide an API to set the
> > coredump
> > mode from the platform driver, the same way
> > rproc_coredump_set_elf_info() works.
> > That will prevent breaking a fair amount of user space code...
> > 
> > Let me know if that can work for you.
> > 
> > Thanks,
> > Mathieu
> > 
> Hi Mathieu,
> That works for product configuration but that would still limit internal
> testing. Since there is also restriction on accessing debugfs through
> userspace code, automation won't be able to run recovery/coredump tests.

Ok, please spinoff a new version that follows the guidelines above and we can
restart the conversation from there. 

> Only other way for us would be to provide these sysfs entries through the
> platform drivers locally but that would create a lot of mess/redundancy.
> 

Right, this is definitely not the right way to proceed.

> > > '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.
> > > 
> > > 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(-)
> > > 
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum,
> > > a Linux Foundation Collaborative Project
> > >