Re: [PATCH v2 3/5] soc: qcom: socinfo: Expose custom attributes
From: Laurent Pinchart
Date: Fri Feb 22 2019 - 04:51:59 EST
On Fri, Feb 22, 2019 at 08:16:16AM +0100, Greg KH wrote:
> On Fri, Feb 22, 2019 at 12:13:59AM +0200, Laurent Pinchart wrote:
> > On Thu, Feb 21, 2019 at 07:57:42AM -0800, Bjorn Andersson wrote:
> > > On Thu 21 Feb 04:18 PST 2019, Laurent Pinchart wrote:
> > > > On Wed, Feb 20, 2019 at 10:28:29AM +0530, Vaishali Thakkar wrote:
> > > > > The Qualcomm socinfo provides a number of additional attributes,
> > > > > add these to the socinfo driver and expose them via debugfs
> > > > > functionality.
> > > >
> > > > What is the use case for these attributes ? I fear they will be used in
> > > > production systems, and that would require debugfs in production, which
> > > > isn't a good idea. If you need to expose those attributes for anything
> > > > else than debugging then we need a proper API, likely sysfs-based.
> > >
> > > The use case of these attributes, beyond development/debugging, are
> > > unfortunately somewhat unknown and is the reason why they where moved to
> > > debugfs from the earlier attempts to upstream this.
> > >
> > > I think the production requirements at hand prohibits debugfs to be
> > > present, so attributes that are required beyond development/debugging
> > > purposes would have to be migrated out to sysfs - but the idea here is
> > > that such migration would have come with the missing motivation to add
> > > them there today.
> > If the use case is just debug/development, would it be enough to print
> > this information in the kernel log at boot time ? I may be a bit
> > paranoid, but I always worry about API abuse :-(
> Putting stuff in debugfs should be fine. No system should ever rely on
> debugfs for a properly running system as it is being disabled on almost
> all "sane" systems (Android included). If a vendor relies on this
> information for a properly working system, then it does not belong in
There's certainly no disagreement about that, my concern is about
vendors who will enable debugfs to access information they need just
because it's there. Do I assume correctly we can "break the debugfs ABI"
in mainline by changing the format of the information if needed ?