From: Leon Romanovsky <leon@kernel.org>
To: Parav Pandit <parav@nvidia.com>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
"kuba@kernel.org" <kuba@kernel.org>,
"parav@mellanox.com" <parav@mellanox.com>,
"tiwai@suse.de" <tiwai@suse.de>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
"ranjani.sridharan@linux.intel.com"
<ranjani.sridharan@linux.intel.com>,
"fred.oh@linux.intel.com" <fred.oh@linux.intel.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"dledford@redhat.com" <dledford@redhat.com>,
"broonie@kernel.org" <broonie@kernel.org>,
Jason Gunthorpe <jgg@nvidia.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"Ertman, David M" <david.m.ertman@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"Saleem, Shiraz" <shiraz.saleem@intel.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"Patil, Kiran" <kiran.patil@intel.com>
Subject: Re: [PATCH v2 1/6] Add ancillary bus support
Date: Thu, 8 Oct 2020 08:26:23 +0300 [thread overview]
Message-ID: <20201008052623.GB13580@unreal> (raw)
In-Reply-To: <BY5PR12MB43222FD5959E490E331D680ADC0B0@BY5PR12MB4322.namprd12.prod.outlook.com>
On Thu, Oct 08, 2020 at 04:56:01AM +0000, Parav Pandit wrote:
>
>
> > From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > Sent: Thursday, October 8, 2020 3:20 AM
> >
> >
> > On 10/7/20 4:22 PM, Ertman, David M wrote:
> > >> -----Original Message-----
> > >> From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > >> Sent: Wednesday, October 7, 2020 1:59 PM
> > >> To: Ertman, David M <david.m.ertman@intel.com>; Parav Pandit
> > >> <parav@nvidia.com>; Leon Romanovsky <leon@kernel.org>
> > >> Cc: 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; Jason Gunthorpe
> > >> <jgg@nvidia.com>; gregkh@linuxfoundation.org; kuba@kernel.org;
> > >> Williams, Dan J <dan.j.williams@intel.com>; Saleem, Shiraz
> > >> <shiraz.saleem@intel.com>; davem@davemloft.net; Patil, Kiran
> > >> <kiran.patil@intel.com>
> > >> Subject: Re: [PATCH v2 1/6] Add ancillary bus support
> > >>
> > >>
> > >>
> > >>>> Below is most simple, intuitive and matching with core APIs for
> > >>>> name and design pattern wise.
> > >>>> init()
> > >>>> {
> > >>>> err = ancillary_device_initialize();
> > >>>> if (err)
> > >>>> return ret;
> > >>>>
> > >>>> err = ancillary_device_add();
> > >>>> if (ret)
> > >>>> goto err_unwind;
> > >>>>
> > >>>> err = some_foo();
> > >>>> if (err)
> > >>>> goto err_foo;
> > >>>> return 0;
> > >>>>
> > >>>> err_foo:
> > >>>> ancillary_device_del(adev);
> > >>>> err_unwind:
> > >>>> ancillary_device_put(adev->dev);
> > >>>> return err;
> > >>>> }
> > >>>>
> > >>>> cleanup()
> > >>>> {
> > >>>> ancillary_device_de(adev);
> > >>>> ancillary_device_put(adev);
> > >>>> /* It is common to have a one wrapper for this as
> > >>>> ancillary_device_unregister().
> > >>>> * This will match with core device_unregister() that has precise
> > >>>> documentation.
> > >>>> * but given fact that init() code need proper error unwinding,
> > >>>> like above,
> > >>>> * it make sense to have two APIs, and no need to export another
> > >>>> symbol for unregister().
> > >>>> * This pattern is very easy to audit and code.
> > >>>> */
> > >>>> }
> > >>>
> > >>> I like this flow +1
> > >>>
> > >>> But ... since the init() function is performing both device_init and
> > >>> device_add - it should probably be called ancillary_device_register,
> > >>> and we are back to a single exported API for both register and
> > >>> unregister.
> > >>
> > >> Kind reminder that we introduced the two functions to allow the
> > >> caller to know if it needed to free memory when initialize() fails,
> > >> and it didn't need to free memory when add() failed since
> > >> put_device() takes care of it. If you have a single init() function
> > >> it's impossible to know which behavior to select on error.
> > >>
> > >> I also have a case with SoundWire where it's nice to first
> > >> initialize, then set some data and then add.
> > >>
> > >
> > > The flow as outlined by Parav above does an initialize as the first
> > > step, so every error path out of the function has to do a
> > > put_device(), so you would never need to manually free the memory in
> > the setup function.
> > > It would be freed in the release call.
> >
> > err = ancillary_device_initialize();
> > if (err)
> > return ret;
> >
> > where is the put_device() here? if the release function does any sort of
> > kfree, then you'd need to do it manually in this case.
> Since device_initialize() failed, put_device() cannot be done here.
> So yes, pseudo code should have shown,
> if (err) {
> kfree(adev);
> return err;
> }
>
> If we just want to follow register(), unregister() pattern,
>
> Than,
>
> ancillar_device_register() should be,
>
> /**
> * ancillar_device_register() - register an ancillary device
> * NOTE: __never directly free @adev after calling this function, even if it returned
> * an error. Always use ancillary_device_put() to give up the reference initialized by this function.
> * This note matches with the core and caller knows exactly what to be done.
> */
> ancillary_device_register()
> {
> device_initialize(&adev->dev);
> if (!dev->parent || !adev->name)
> return -EINVAL;
> if (!dev->release && !(dev->type && dev->type->release)) {
> /* core is already capable and throws the warning when release callback is not set.
> * It is done at drivers/base/core.c:1798.
> * For NULL release it says, "does not have a release() function, it is broken and must be fixed"
> */
> return -EINVAL;
> }
> err = dev_set_name(adev...);
> if (err) {
> /* kobject_release() -> kobject_cleanup() are capable to detect if name is set/ not set
> * and free the const if it was set.
> */
> return err;
> }
> err = device_add(&adev->dev);
> If (err)
> return err;
> }
>
> Caller code:
> init()
> {
> adev = kzalloc(sizeof(*foo_adev)..);
> if (!adev)
> return -ENOMEM;
> err = ancillary_device_register(&adev);
> if (err)
> goto err;
>
> err:
> ancillary_device_put(&adev);
> return err;
> }
>
> cleanup()
> {
> ancillary_device_unregister(&adev);
> }
>
> Above pattern is fine too matching the core.
>
> If I understand Leon correctly, he prefers simple register(), unregister() pattern.
> If, so it should be explicit register(), unregister() API.
This is my summary
https://lore.kernel.org/linux-rdma/20201008052137.GA13580@unreal
The API should be symmetric.
Thanks
next prev parent reply other threads:[~2020-10-08 5:27 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
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 [this message]
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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