From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: [Linux-fbdev-devel] [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins Date: Wed, 26 Nov 2008 13:08:57 +0100 (CET) Message-ID: References: <12276535632759-git-send-email-jayakumar.lkml@gmail.com> <492D125D.5010607@teltonika.lt> <45a44e480811260118v440716bbqa8d37c8b696c148a@mail.gmail.com> <45a44e480811260225k5dc2bedal41ccac33626f3b4c@mail.gmail.com> Mime-Version: 1.0 Return-path: In-Reply-To: <45a44e480811260225k5dc2bedal41ccac33626f3b4c@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jaya Kumar Cc: Paulius Zaleckas , David Brownell , linux-fbdev-devel@lists.sourceforge.net, Haavard Skinnemoen , Greg KH , linux-kernel@vger.kernel.org, David Brownell , Ben Gardner , Eric Miao , Philipp Zabel , Sam Ravnborg , linux-arm-kernel@lists.arm.linux.org.uk, Russell King On Wed, 26 Nov 2008, Jaya Kumar wrote: > On Wed, Nov 26, 2008 at 5:08 AM, Geert Uytterhoeven > wrote: > > On Wed, 26 Nov 2008, Jaya Kumar wrote: > >> On Wed, Nov 26, 2008 at 4:09 AM, Paulius Zaleckas > >> wrote: > >> > Jaya Kumar wrote: > >> >> * @to_irq: optional hook supporting non-static gpio_to_irq() mappings; > >> >> * implementation may not sleep > >> >> * @dbg_show: optional routine to show contents in debugfs; default code > >> >> @@ -84,6 +86,9 @@ struct gpio_chip { > >> >> unsigned offset, int value); > >> >> void (*set)(struct gpio_chip *chip, > >> >> unsigned offset, int value); > >> >> + void (*set_bus)(struct gpio_chip *chip, > >> >> + unsigned offset, int values, > >> > > >> > I think values should be unsigned > >> > >> Okay, can do but it is unusual no? since set uses int value, i figured > >> set_bus should be similar right? > > > > ->set() sets one pin, right? So it's either 0 or 1. > > > > ->set_bus() sets multiple pins. With `int', it will fail for bit 31, as that's > > the sign bit. > > I'm not sure I understood this. I imagine the usage will be like > > int values = 0x8000_0000; > set_bus(..., start_pin, values); > > write_32(register, values); // will still work to set bit 31 Tehcnically, it will work. But it's more confusing if it's int. > (values >> 31) == 1; However, be careful with shifts, as right shifts on signed values will duplicate te sign bit. > > Perhaps you even want u32, to make it clear what's the maximum number of pins > > you can set in one shot? > > Yes, I agree, I will change to use u32 as it is then explicit. OK. Thx! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds