From: Leon Romanovsky <leon@kernel.org>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: Dave Ertman <david.m.ertman@intel.com>,
alsa-devel@alsa-project.org, parav@mellanox.com, tiwai@suse.de,
netdev@vger.kernel.org, ranjani.sridharan@linux.intel.com,
fred.oh@linux.intel.com, linux-rdma@vger.kernel.org,
dledford@redhat.com, broonie@kernel.org, jgg@nvidia.com,
gregkh@linuxfoundation.org, kuba@kernel.org,
dan.j.williams@intel.com, shiraz.saleem@intel.com,
davem@davemloft.net, kiran.patil@intel.com
Subject: Re: [PATCH v2 1/6] Add ancillary bus support
Date: Tue, 6 Oct 2020 20:02:41 +0300 [thread overview]
Message-ID: <20201006170241.GM1874917@unreal> (raw)
In-Reply-To: <b4f6b5d1-2cf4-ae7a-3e57-b66230a58453@linux.intel.com>
On Tue, Oct 06, 2020 at 10:18:07AM -0500, Pierre-Louis Bossart wrote:
> Thanks for the review Leon.
>
> > > Add support for the Ancillary Bus, ancillary_device and ancillary_driver.
> > > It enables drivers to create an ancillary_device and bind an
> > > ancillary_driver to it.
> >
> > I was under impression that this name is going to be changed.
>
> It's part of the opens stated in the cover letter.
ok, so what are the variants?
system bus (sysbus), sbsystem bus (subbus), crossbus ?
>
> [...]
>
> > > + const struct my_driver my_drv = {
> > > + .ancillary_drv = {
> > > + .driver = {
> > > + .name = "myancillarydrv",
> >
> > Why do we need to give control over driver name to the driver authors?
> > It can be problematic if author puts name that already exists.
>
> Good point. When I used the ancillary_devices for my own SoundWire test, the
> driver name didn't seem specifically meaningful but needed to be set to
> something, what mattered was the id_table. Just thinking aloud, maybe we can
> add prefixing with KMOD_BUILD, as we've done already to avoid collisions
> between device names?
IMHO, it shouldn't be controlled by the drivers at all and need to have
kernel module name hardwired. Users will use it later for various
bind/unbind/autoprobe tricks and it will give predictability for them.
>
> [...]
>
> > > +int __ancillary_device_add(struct ancillary_device *ancildev, const char *modname)
> > > +{
> > > + struct device *dev = &ancildev->dev;
> > > + int ret;
> > > +
> > > + if (!modname) {
> > > + pr_err("ancillary device modname is NULL\n");
> > > + return -EINVAL;
> > > + }
> > > +
> > > + ret = dev_set_name(dev, "%s.%s.%d", modname, ancildev->name, ancildev->id);
> > > + if (ret) {
> > > + pr_err("ancillary device dev_set_name failed: %d\n", ret);
> > > + return ret;
> > > + }
> > > +
> > > + ret = device_add(dev);
> > > + if (ret)
> > > + dev_err(dev, "adding ancillary device failed!: %d\n", ret);
> > > +
> > > + return ret;
> > > +}
> >
> > Sorry, but this is very strange API that requires users to put
> > internal call to "dev" that is buried inside "struct ancillary_device".
> >
> > For example in your next patch, you write this "put_device(&cdev->ancildev.dev);"
> >
> > I'm pretty sure that the amount of bugs in error unwind will be
> > astonishing, so if you are doing wrappers over core code, better do not
> > pass complexity to the users.
>
> In initial reviews, there was pushback on adding wrappers that don't do
> anything except for a pointer indirection.
>
> Others had concerns that the API wasn't balanced and blurring layers.
Are you talking about internal review or public?
If it is public, can I get a link to it?
>
> Both points have merits IMHO. Do we want wrappers for everything and
> completely hide the low-level device?
This API is partially obscures low level driver-core code and needs to
provide clear and proper abstractions without need to remember about
put_device. There is already _add() interface why don't you do
put_device() in it?
>
> >
> > > +EXPORT_SYMBOL_GPL(__ancillary_device_add);
> > > +
> > > +static int ancillary_probe_driver(struct device *dev)
> > > +{
> > > + struct ancillary_driver *ancildrv = to_ancillary_drv(dev->driver);
> > > + struct ancillary_device *ancildev = to_ancillary_dev(dev);
> > > + int ret;
> > > +
> > > + ret = dev_pm_domain_attach(dev, true);
> > > + if (ret) {
> > > + dev_warn(dev, "Failed to attach to PM Domain : %d\n", ret);
> > > + return ret;
> > > + }
> > > +
> > > + ret = ancildrv->probe(ancildev, ancillary_match_id(ancildrv->id_table, ancildev));
> >
> > I don't think that you need to call ->probe() if ancillary_match_id()
> > returned NULL and probably that check should be done before
> > dev_pm_domain_attach().
>
> we'll look into this.
>
> >
> > > + if (ret)
> > > + dev_pm_domain_detach(dev, true);
> > > +
> > > + return ret;
> > > +}
> > > +
> > > +static int ancillary_remove_driver(struct device *dev)
> > > +{
> > > + struct ancillary_driver *ancildrv = to_ancillary_drv(dev->driver);
> > > + struct ancillary_device *ancildev = to_ancillary_dev(dev);
> > > + int ret;
> > > +
> > > + ret = ancildrv->remove(ancildev);
> > > + dev_pm_domain_detach(dev, true);
> > > +
> > > + return ret;
> >
> > You returned an error to user and detached from PM, what will user do
> > with this information? Should user ignore it? retry?
>
> That comment was also provided in earlier reviews. In practice the error is
> typically ignored so there was a suggestion to move the return type to void,
> that could be done if this was desired by the majority.
+1 from me.
>
> [...]
>
> > > diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> > > index 5b08a473cdba..7d596dc30833 100644
> > > --- a/include/linux/mod_devicetable.h
> > > +++ b/include/linux/mod_devicetable.h
> > > @@ -838,4 +838,12 @@ struct mhi_device_id {
> > > kernel_ulong_t driver_data;
> > > };
> > >
> > > +#define ANCILLARY_NAME_SIZE 32
> > > +#define ANCILLARY_MODULE_PREFIX "ancillary:"
> > > +
> > > +struct ancillary_device_id {
> > > + char name[ANCILLARY_NAME_SIZE];
> >
> > I hope that this be enough.
>
> Are you suggesting a different value to allow for a longer string?
I have no idea, but worried that there were no checks at all if name is
more than 32. Maybe compiler warn about it?
Thanks
next prev parent reply other threads:[~2020-10-06 17:02 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 18:24 [PATCH v2 0/6] Ancillary bus implementation and SOF multi-client support Dave Ertman
2020-10-05 18:24 ` [PATCH v2 1/6] Add ancillary bus support Dave Ertman
2020-10-06 7:18 ` Leon Romanovsky
2020-10-06 15:18 ` Pierre-Louis Bossart
2020-10-06 17:02 ` Leon Romanovsky [this message]
2020-10-06 17:09 ` Parav Pandit
2020-10-06 17:26 ` Leon Romanovsky
2020-10-06 17:41 ` Saleem, Shiraz
2020-10-06 19:20 ` Leon Romanovsky
2020-10-07 2:49 ` Dan Williams
2020-10-07 13:09 ` Saleem, Shiraz
2020-10-07 13:36 ` Leon Romanovsky
2020-10-07 18:55 ` Dan Williams
2020-10-07 20:01 ` Ertman, David M
2020-10-06 18:35 ` Ranjani Sridharan
2020-10-06 17:50 ` Saleem, Shiraz
2020-10-07 18:06 ` Ertman, David M
2020-10-07 19:26 ` Leon Romanovsky
2020-10-07 19:53 ` Ertman, David M
2020-10-07 19:57 ` Ertman, David M
2020-10-07 20:17 ` Parav Pandit
2020-10-07 20:46 ` Ertman, David M
2020-10-07 20:59 ` Pierre-Louis Bossart
2020-10-07 21:22 ` Ertman, David M
2020-10-07 21:49 ` Pierre-Louis Bossart
2020-10-08 4:56 ` Parav Pandit
2020-10-08 5:26 ` Leon Romanovsky
2020-10-08 7:14 ` Parav Pandit
2020-10-08 7:45 ` Leon Romanovsky
2020-10-08 9:45 ` Parav Pandit
2020-10-08 10:17 ` Leon Romanovsky
2020-10-08 13:29 ` Pierre-Louis Bossart
2020-10-09 11:40 ` Leon Romanovsky
2020-10-08 16:54 ` Ertman, David M
2020-10-08 17:35 ` Parav Pandit
2020-10-08 18:13 ` Ertman, David M
2020-10-08 5:21 ` Leon Romanovsky
2020-10-08 6:32 ` Dan Williams
2020-10-08 7:00 ` Leon Romanovsky
2020-10-08 7:38 ` Dan Williams
2020-10-08 7:50 ` gregkh
2020-10-08 11:10 ` Parav Pandit
2020-10-08 16:39 ` Ertman, David M
2020-10-08 8:00 ` Leon Romanovsky
2020-10-08 8:09 ` Dan Williams
2020-10-08 16:42 ` Ertman, David M
2020-10-08 17:21 ` Leon Romanovsky
2020-10-08 18:25 ` Ertman, David M
2020-10-07 20:30 ` Ertman, David M
2020-10-07 20:18 ` Ertman, David M
2020-10-06 17:23 ` Leon Romanovsky
2020-10-06 17:45 ` Saleem, Shiraz
2020-10-08 22:04 ` Ertman, David M
2020-10-08 22:41 ` Dan Williams
2020-10-09 14:26 ` Pierre-Louis Bossart
2020-10-09 19:22 ` Dan Williams
2020-10-09 19:39 ` Pierre-Louis Bossart
2020-10-12 18:34 ` Ertman, David M
2020-10-08 17:20 ` Leon Romanovsky
2020-10-08 17:28 ` Ertman, David M
2020-10-05 18:24 ` [PATCH v2 2/6] ASoC: SOF: Introduce descriptors for SOF client Dave Ertman
2020-10-13 1:05 ` Randy Dunlap
2020-10-13 1:31 ` Pierre-Louis Bossart
2020-10-13 1:55 ` Randy Dunlap
2020-10-13 1:56 ` Randy Dunlap
2020-10-13 15:08 ` Pierre-Louis Bossart
2020-10-13 19:35 ` Randy Dunlap
2020-10-13 19:57 ` Pierre-Louis Bossart
2020-10-05 18:24 ` [PATCH v2 3/6] ASoC: SOF: Create client driver for IPC test Dave Ertman
2020-10-05 18:24 ` [PATCH v2 4/6] ASoC: SOF: ops: Add ops for client registration Dave Ertman
2020-10-05 18:24 ` [PATCH v2 5/6] ASoC: SOF: Intel: Define " Dave Ertman
2020-10-05 18:24 ` [PATCH v2 6/6] ASoC: SOF: debug: Remove IPC flood test support in SOF core Dave Ertman
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