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Date: Fri, 31 Jan 2020 10:36:46 +0100 From: 'Greg KH' <gregkh@...uxfoundation.org> To: Rajan Vaja <RAJANV@...inx.com> Cc: Jolly Shah <JOLLYS@...inx.com>, "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>, "mingo@...nel.org" <mingo@...nel.org>, "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>, "sudeep.holla@....com" <sudeep.holla@....com>, "hkallweit1@...il.com" <hkallweit1@...il.com>, "keescook@...omium.org" <keescook@...omium.org>, "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>, Michal Simek <michals@...inx.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 1/4] firmware: xilinx: Add sysfs interface On Fri, Jan 31, 2020 at 09:05:15AM +0000, Rajan Vaja wrote: > Hi Greg, > > > -----Original Message----- > > From: Greg KH <gregkh@...uxfoundation.org> > > Sent: 31 January 2020 11:41 AM > > To: Jolly Shah <JOLLYS@...inx.com> > > Cc: ard.biesheuvel@...aro.org; mingo@...nel.org; matt@...eblueprint.co.uk; > > sudeep.holla@....com; hkallweit1@...il.com; keescook@...omium.org; > > dmitry.torokhov@...il.com; Michal Simek <michals@...inx.com>; Rajan Vaja > > <RAJANV@...inx.com>; linux-arm-kernel@...ts.infradead.org; linux- > > kernel@...r.kernel.org > > Subject: Re: [PATCH v2 1/4] firmware: xilinx: Add sysfs interface > > > > EXTERNAL EMAIL > > > > On Thu, Jan 30, 2020 at 11:59:03PM +0000, Jolly Shah wrote: > > > Hi Greg, > > > > > > On 1/27/20, 10:28 PM, "linux-kernel-owner@...r.kernel.org on behalf of Greg > > KH" <linux-kernel-owner@...r.kernel.org on behalf of > > gregkh@...uxfoundation.org> wrote: > > > > > > On Mon, Jan 27, 2020 at 11:01:27PM +0000, Jolly Shah wrote: > > > > > > > + ret = kstrtol(tok, 16, &value); > > > > > > > + if (ret) { > > > > > > > + ret = -EFAULT; > > > > > > > + goto err; > > > > > > > + } > > > > > > > + > > > > > > > + ret = eemi_ops->ioctl(0, read_ioctl, reg, 0, ret_payload); > > > > > > > > > > > > This feels "tricky", if you tie this to the device you have your driver > > > > > > bound to, will this make it easier instead of having to go through the > > > > > > ioctl callback? > > > > > > > > > > > > > > > > GGS(general global storage) registers are in PMU space and linux > > doesn't have access to it > > > > > Hence ioctl is used. > > > > > > > > Why not just a "real" call to the driver to make this type of reading? > > > > You don't have ioctls within the kernel for other drivers to call, > > > > that's not needed at all. > > > > > > > > these registers are for users and for special needs where users wants > > > > to retain values over resets. but as they belong to PMU address space, > > > > these interface APIs are provided. They don’t allow access to any > > > > other registers. > > > > > > That's not the issue here. The issue is you are using an "internal" > > > ioctl, instead just make a "real" call. > > > > > > Sorry I am not clear. Do you mean that we should use linux standard > > > ioctl interface instead of internal ioctl by mentioning "real" ? > > > > No, you should just make a "real" function call to the exact thing you > > want to do. Not have an internal multi-plexor ioctl() call that others > > then call. This isn't a microkernel :) > [Rajan] Sorry for multiple back and forth but as I understand, you are suggesting to create a new API for > Read/write of GGS register instead of using PM_IOCTL API (eemi_ops->ioctl) for multiple purpose. Is my understanding correct? That is correct.
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