From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs Date: Wed, 13 Apr 2016 08:43:29 -0700 Message-ID: <20160413154328.GR5995@atomide.com> References: <1460530865-29085-1-git-send-email-j-keerthy@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1460530865-29085-1-git-send-email-j-keerthy@ti.com> Sender: linux-kernel-owner@vger.kernel.org To: Keerthy Cc: linus.walleij@linaro.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, t-kristo@ti.com, nsekhar@ti.com List-Id: linux-omap@vger.kernel.org * Keerthy [160413 00:03]: > pcs_parse_bits_in_pinctrl_entry uses ffs which gives bit indices > ranging from 1 to MAX. This leads to a corner case where we try to request > the pin number = MAX and fails. > > bit_pos value is being calculted using ffs. pin_num_from_lsb uses > bit_pos value. pins array is populated with: > > pin + pin_num_from_lsb. > > The above is 1 more than usual bit indices as bit_pos uses ffs to compute > first set bit. Hence the last of the pins array is populated with the MAX > value and not MAX - 1 which causes error when we call pin_request. Hmm that sounds like a bug to me, just one comment below. > --- a/drivers/pinctrl/pinctrl-single.c > +++ b/drivers/pinctrl/pinctrl-single.c > @@ -1323,9 +1323,9 @@ static int pcs_parse_bits_in_pinctrl_entry(struct pcs_device *pcs, > > /* Parse pins in each row from LSB */ > while (mask) { > - bit_pos = ffs(mask); > + bit_pos = __ffs(mask); > pin_num_from_lsb = bit_pos / pcs->bits_per_pin; > - mask_pos = ((pcs->fmask) << (bit_pos - 1)); > + mask_pos = ((pcs->fmask) << bit_pos); > val_pos = val & mask_pos; > submask = mask & mask_pos; Can you please also change the pcs->fshift = ffs(pcs->fmask) - 1 to use __ffs to avoid confusion? Regards, Tony