From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rob Herring <robh+dt@kernel.org>,
Daniel Scally <djrscally@gmail.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Subject: Re: [PATCH v4 1/7] device property: Helper to match multiple connections
Date: Mon, 7 Mar 2022 11:13:28 -0800 [thread overview]
Message-ID: <YiZZWN1FgnWxBCuN@ripper> (raw)
In-Reply-To: <YiXZBMG7cK6Cm7wP@smile.fi.intel.com>
On Mon 07 Mar 02:05 PST 2022, Andy Shevchenko wrote:
> On Sun, Mar 06, 2022 at 07:40:34PM -0800, Bjorn Andersson wrote:
> > In some cases multiple connections with the same connection id
> > needs to be resolved from a fwnode graph.
> >
> > One such example is when separate hardware is used for performing muxing
> > and/or orientation switching of the SuperSpeed and SBU lines in a USB
> > Type-C connector. In this case the connector needs to belong to a graph
> > with multiple matching remote endpoints, and the Type-C controller needs
> > to be able to resolve them both.
> >
> > Add a new API that allows this kind of lookup.
>
> Thanks for the update!
>
> First of all, I have noticed that subject misses the verb, something like Add
> or Introduce.
>
Will update accordingly.
> ...
>
> > +/**
> > + * fwnode_connection_find_matches - Find connections from a device node
> > + * @fwnode: Device node with the connection
> > + * @con_id: Identifier for the connection
> > + * @data: Data for the match function
> > + * @match: Function to check and convert the connection description
> > + * @matches: Array of pointers to fill with matches
>
> (Optional) array...
>
Ditto.
> > + * @matches_len: Length of @matches
> > + *
> > + * Find up to @matches_len connections with unique identifier @con_id between
> > + * @fwnode and other device nodes. @match will be used to convert the
> > + * connection description to data the caller is expecting to be returned
> > + * through the @matches array.
>
> > + * If @matches is NULL @matches_len is ignored and the total number of resolved
> > + * matches is returned.
>
> I would require matches_len to be 0, see below.
>
> > + * Return: Number of matches resolved, or negative errno.
> > + */
> > +int fwnode_connection_find_matches(struct fwnode_handle *fwnode,
> > + const char *con_id, void *data,
> > + devcon_match_fn_t match,
> > + void **matches, unsigned int matches_len)
> > +{
> > + unsigned int count_graph;
> > + unsigned int count_ref;
> > +
> > + if (!fwnode || !match)
> > + return -EINVAL;
> > +
> > + count_graph = fwnode_graph_devcon_matches(fwnode, con_id, data, match,
> > + matches, matches_len);
>
> > + if (matches) {
> > + matches += count_graph;
> > + matches_len -= count_graph;
> > + }
>
> So, the valid case is matches != NULL and matches_len == 0. For example, when
> we have run something previously on the buffer and it becomes full.
>
> In this case we have carefully handle this case.
>
> if (matches) {
> matches += count_graph;
> if (matches_len)
> matches_len -= count_graph;
When matches is non-NULL, both the sub-functions are limited by
matches_len and as such count_graph <= matches_len.
As such matches_len >= 0.
In the event that the originally passed matches_len was 0, then
count_graph will be 0 and matches_len will remain 0.
I therefor don't see that this additional check changes things.
> }
>
> Seems it can be also
>
> if (matches)
> matches += count_graph;
>
> if (matches_len)
> matches_len -= count_graph;
We covered the case of matches && (matches_len || !matches_len) above.
For the case of !matches && matches_len, this added conditional would
cause matches_len to be extra ignored by keeping it at 0, but per
kernel-doc and implementation we ignore all other values already.
Note that this is in contrast from vsnprintf() where the code will
continue to produce results, only store the first "matches_len"
entires and return the final count.
Unfortunately we can't follow such semantics here, instead it is clearly
documented in the kernel-doc that @matches_len is ignored when @matches
is NULL.
So unless I'm missing something I don't see what you gain over keeping
the check on only matches.
>
> That said, do we have a test cases for this?
>
I looked briefly at adding some kunit tests for this, but was discourage
by the prospect of building up the graphs to run the tests against.
Regards,
Bjorn
> > + count_ref = fwnode_devcon_matches(fwnode, con_id, data, match,
> > + matches, matches_len);
> > +
> > + return count_graph + count_ref;
> > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
prev parent reply other threads:[~2022-03-07 19:11 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 3:40 [PATCH v4 1/7] device property: Helper to match multiple connections Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 2/7] device property: Use multi-connection matchers for single case Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 3/7] usb: typec: mux: Check dev_set_name() return value Bjorn Andersson
2022-03-07 10:08 ` Andy Shevchenko
2022-03-07 14:33 ` Bjorn Andersson
2022-03-07 14:52 ` Heikki Krogerus
2022-03-07 3:40 ` [PATCH v4 4/7] usb: typec: mux: Introduce indirection Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 5/7] usb: typec: mux: Allow multiple mux_devs per mux Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 6/7] dt-bindings: usb: Add binding for fcs,fsa4480 Bjorn Andersson
2022-03-07 3:40 ` [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver Bjorn Andersson
2022-03-07 10:16 ` Andy Shevchenko
2022-03-07 14:48 ` Bjorn Andersson
2022-03-07 16:13 ` Andy Shevchenko
2022-03-07 21:04 ` Bjorn Andersson
2022-03-07 22:13 ` Andy Shevchenko
2022-03-08 0:01 ` Bjorn Andersson
2022-03-07 10:05 ` [PATCH v4 1/7] device property: Helper to match multiple connections Andy Shevchenko
2022-03-07 19:13 ` Bjorn Andersson [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YiZZWN1FgnWxBCuN@ripper \
--to=bjorn.andersson@linaro.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=devicetree@vger.kernel.org \
--cc=djrscally@gmail.com \
--cc=dmitry.baryshkov@linaro.org \
--cc=hdegoede@redhat.com \
--cc=heikki.krogerus@linux.intel.com \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=robh+dt@kernel.org \
--cc=sakari.ailus@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).