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Date: Mon, 17 Feb 2020 16:12:41 +0000 From: Vitor Soares <Vitor.Soares@...opsys.com> To: gregkh <gregkh@...uxfoundation.org> CC: Boris Brezillon <boris.brezillon@...labora.com>, Arnd Bergmann <arnd@...db.de>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>, Jose Abreu <Jose.Abreu@...opsys.com>, "Joao Pinto" <Joao.Pinto@...opsys.com>, Wolfram Sang <wsa@...-dreams.de>, "Boris Brezillon" <bbrezillon@...nel.org>, Mark Brown <broonie@...nel.org> Subject: RE: [RFC v2 0/4] Introduce i3c device userspace interface From: gregkh <gregkh@...uxfoundation.org> Date: Mon, Feb 17, 2020 at 16:03:45 > On Mon, Feb 17, 2020 at 03:55:08PM +0000, Vitor Soares wrote: > > Hi, > > > > From: Boris Brezillon <boris.brezillon@...labora.com> > > Date: Mon, Feb 17, 2020 at 15:36:22 > > > > > On Mon, 17 Feb 2020 16:06:45 +0100 > > > Arnd Bergmann <arnd@...db.de> wrote: > > > > > > > On Mon, Feb 17, 2020 at 3:51 PM Boris Brezillon > > > > <boris.brezillon@...labora.com> wrote: > > > > > Sorry for taking so long to reply, and thanks for working on that topic. > > > > > > > > > > On Wed, 29 Jan 2020 13:17:31 +0100 > > > > > Vitor Soares <Vitor.Soares@...opsys.com> wrote: > > > > > > > > > > > For today there is no way to use i3c devices from user space and > > > > > > the introduction of such API will help developers during the i3c device > > > > > > or i3c host controllers development. > > > > > > > > > > > > The i3cdev module is highly based on i2c-dev and yet I tried to address > > > > > > the concerns raised in [1]. > > > > > > > > > > > > NOTES: > > > > > > - The i3cdev dynamically request an unused major number. > > > > > > > > > > > > - The i3c devices are dynamically exposed/removed from dev/ folder based > > > > > > on if they have a device driver bound to it. > > > > > > > > > > May I ask why you need to automatically bind devices to the i3cdev > > > > > driver when they don't have a driver matching the device id > > > > > loaded/compiled-in? If we get the i3c subsystem to generate proper > > > > > uevents we should be able to load the i3cdev module and bind the device > > > > > to this driver using a udev rule. > > > > > > > > I think that would require manual configuration to ensure that the correct > > > > set of devices get bound to either the userspace driver or an in-kernel > > > > driver. > > > > > > Hm, isn't that what udev is supposed to do anyway? Remember that > > > I3C devices expose a manufacturer and part-id (which are similar to the > > > USB vendor and product ids), so deciding when an I3C device should be > > > bound to the i3cdev driver should be fairly easy, and that's a > > > per-device decision anyway. > > > > > > > The method from the current patch series is more complicated, > > > > but it means that any device can be accessed by the user space driver > > > > as long as it's not already owned by a kernel driver. > > > > > > Well, I'm more worried about the extra churn this auto-binding logic > > > might create for the common 'on-demand driver loading' use case. At > > > first, there's no driver matching a specific device, but userspace > > > might load one based on the uevents it receives. With the current > > > approach, that means we'd first have to unbind the device before > > > loading the driver. AFAICT, no other subsystem does that. > > > > I'm about to finish v3 (today or tomorrow) and I think I fixed all > > concerns rise during v2. I would like you to see that version before any > > change. > > Why are there so many "RFC" series here? I treat "RFC" as "I don't > really like this patch but I'm throwing it out there for others to look > at if they care". No RFC should ever go on beyond a v1 My bad ☹. > as obviously you > think this is good enough by now, right? Yes and I really appreciate the feedback that leads me to this v3. > > Also, I almost never review RFC patches, we have enough "real" patches > to review as it is :) > > thanks, > > greg k-h Thanks for your advice. Best regards, Vitor Soares
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