From: Baolin Wang <baolin.wang7@gmail.com> To: Lee Jones <lee.jones@linaro.org> Cc: Johan Hovold <johan@kernel.org>, Orson Zhai <orsonzhai@gmail.com>, LKML <linux-kernel@vger.kernel.org>, linux-arm-kernel@lists.infradead.org, Chunyan Zhang <zhang.lyra@gmail.com> Subject: Re: [PATCH 4/5] mfd: sprd-sc27xx-spi: Fix divide by zero when allocating register offset/mask Date: Mon, 29 Jun 2020 22:35:06 +0800 [thread overview] Message-ID: <CADBw62r_tkGEr9kHpojAi+fJ+qUqbsc-DQgG1TUAwOdbDXTgNQ@mail.gmail.com> (raw) In-Reply-To: <20200629140137.GK177734@dell> On Mon, Jun 29, 2020 at 10:01 PM Lee Jones <lee.jones@linaro.org> wrote: > > On Mon, 29 Jun 2020, Johan Hovold wrote: > > > On Mon, Jun 29, 2020 at 01:32:14PM +0100, Lee Jones wrote: > > > Since ddata->irqs[] is already zeroed when allocated by devm_kcalloc() and > > > dividing 0 by anything is still 0, there is no need to re-assign > > > ddata->irqs[i].* values. Instead, it should be safe to begin at 1. > > > > > > This fixes the following W=1 warning: > > > > > > drivers/mfd/sprd-sc27xx-spi.c:255 sprd_pmic_probe() debug: sval_binop_unsigned: divide by zero > > > > > > Cc: Orson Zhai <orsonzhai@gmail.com> > > > Cc: Baolin Wang <baolin.wang7@gmail.com> > > > Cc: Chunyan Zhang <zhang.lyra@gmail.com> > > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > > --- > > > drivers/mfd/sprd-sc27xx-spi.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/mfd/sprd-sc27xx-spi.c b/drivers/mfd/sprd-sc27xx-spi.c > > > index c305e941e435c..694a7d429ccff 100644 > > > --- a/drivers/mfd/sprd-sc27xx-spi.c > > > +++ b/drivers/mfd/sprd-sc27xx-spi.c > > > @@ -251,7 +251,7 @@ static int sprd_pmic_probe(struct spi_device *spi) > > > return -ENOMEM; > > > > > > ddata->irq_chip.irqs = ddata->irqs; > > > - for (i = 0; i < pdata->num_irqs; i++) { > > > + for (i = 1; i < pdata->num_irqs; i++) { > > > ddata->irqs[i].reg_offset = i / pdata->num_irqs; > > > ddata->irqs[i].mask = BIT(i % pdata->num_irqs); > > > } > > > > This doesn't look right either. > > > > First, the loop is never executed if num_irqs is zero. > > The point of the patch is that 0 entries are never processed. > > However, what I appear to have overlooked is that BIT(0 % x) is not 0, > it's 1. Yes. > > > Second, the current code looks bogus too as reg_offset is always set to > > zero and mask to BIT(i)... Now the result is correct, since all PMIC irq mask bits are in one register now, which means the reg_offset is always 0 can work well. But I think the logics still can be improved if our PMIC irq numbers are larger than 32 in future. > > Heh. I wonder if/how this was tested. > > I'm going to wait to hear from the authors before attempting to fix > this again. > > Baolin, Could you please clarify this for us please? Yes, see above comments. -- Baolin Wang
WARNING: multiple messages have this Message-ID (diff)
From: Baolin Wang <baolin.wang7@gmail.com> To: Lee Jones <lee.jones@linaro.org> Cc: Orson Zhai <orsonzhai@gmail.com>, Chunyan Zhang <zhang.lyra@gmail.com>, Johan Hovold <johan@kernel.org>, linux-arm-kernel@lists.infradead.org, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 4/5] mfd: sprd-sc27xx-spi: Fix divide by zero when allocating register offset/mask Date: Mon, 29 Jun 2020 22:35:06 +0800 [thread overview] Message-ID: <CADBw62r_tkGEr9kHpojAi+fJ+qUqbsc-DQgG1TUAwOdbDXTgNQ@mail.gmail.com> (raw) In-Reply-To: <20200629140137.GK177734@dell> On Mon, Jun 29, 2020 at 10:01 PM Lee Jones <lee.jones@linaro.org> wrote: > > On Mon, 29 Jun 2020, Johan Hovold wrote: > > > On Mon, Jun 29, 2020 at 01:32:14PM +0100, Lee Jones wrote: > > > Since ddata->irqs[] is already zeroed when allocated by devm_kcalloc() and > > > dividing 0 by anything is still 0, there is no need to re-assign > > > ddata->irqs[i].* values. Instead, it should be safe to begin at 1. > > > > > > This fixes the following W=1 warning: > > > > > > drivers/mfd/sprd-sc27xx-spi.c:255 sprd_pmic_probe() debug: sval_binop_unsigned: divide by zero > > > > > > Cc: Orson Zhai <orsonzhai@gmail.com> > > > Cc: Baolin Wang <baolin.wang7@gmail.com> > > > Cc: Chunyan Zhang <zhang.lyra@gmail.com> > > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > > --- > > > drivers/mfd/sprd-sc27xx-spi.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/mfd/sprd-sc27xx-spi.c b/drivers/mfd/sprd-sc27xx-spi.c > > > index c305e941e435c..694a7d429ccff 100644 > > > --- a/drivers/mfd/sprd-sc27xx-spi.c > > > +++ b/drivers/mfd/sprd-sc27xx-spi.c > > > @@ -251,7 +251,7 @@ static int sprd_pmic_probe(struct spi_device *spi) > > > return -ENOMEM; > > > > > > ddata->irq_chip.irqs = ddata->irqs; > > > - for (i = 0; i < pdata->num_irqs; i++) { > > > + for (i = 1; i < pdata->num_irqs; i++) { > > > ddata->irqs[i].reg_offset = i / pdata->num_irqs; > > > ddata->irqs[i].mask = BIT(i % pdata->num_irqs); > > > } > > > > This doesn't look right either. > > > > First, the loop is never executed if num_irqs is zero. > > The point of the patch is that 0 entries are never processed. > > However, what I appear to have overlooked is that BIT(0 % x) is not 0, > it's 1. Yes. > > > Second, the current code looks bogus too as reg_offset is always set to > > zero and mask to BIT(i)... Now the result is correct, since all PMIC irq mask bits are in one register now, which means the reg_offset is always 0 can work well. But I think the logics still can be improved if our PMIC irq numbers are larger than 32 in future. > > Heh. I wonder if/how this was tested. > > I'm going to wait to hear from the authors before attempting to fix > this again. > > Baolin, Could you please clarify this for us please? Yes, see above comments. -- Baolin Wang _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-06-29 19:23 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-29 12:32 [PATCH 0/5] Last batch of W=1 warning fixes in MFD Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 12:32 ` [PATCH 1/5] mfd: si476x-cmd: Add missing documentation for si476x_cmd_fm_rds_status()'s arg 'report' Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 12:32 ` [PATCH 2/5] mfd: lm3533-ctrlbank: Cap BRIGHTNESS_MAX to 127 since API uses u8 as carrier Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 12:51 ` Johan Hovold 2020-06-29 12:51 ` Johan Hovold 2020-06-29 13:25 ` Lee Jones 2020-06-29 13:25 ` Lee Jones 2020-06-30 8:38 ` Johan Hovold 2020-06-30 8:38 ` Johan Hovold 2020-06-29 12:32 ` [PATCH 3/5] mfd: rave-sp: Fix mistake in 'struct rave_sp_deframer's kerneldoc Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 12:32 ` [PATCH 4/5] mfd: sprd-sc27xx-spi: Fix divide by zero when allocating register offset/mask Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 13:06 ` Johan Hovold 2020-06-29 13:06 ` Johan Hovold 2020-06-29 14:01 ` Lee Jones 2020-06-29 14:01 ` Lee Jones 2020-06-29 14:35 ` Baolin Wang [this message] 2020-06-29 14:35 ` Baolin Wang 2020-06-29 14:43 ` Johan Hovold 2020-06-29 14:43 ` Johan Hovold 2020-06-29 15:08 ` Baolin Wang 2020-06-29 15:08 ` Baolin Wang 2020-06-29 15:45 ` Lee Jones 2020-06-29 15:45 ` Lee Jones 2020-07-01 9:15 ` [PATCH] mfd: sprd-sc27xx-spi: Fix-up bogus IRQ register offset and mask setting Lee Jones 2020-07-01 9:15 ` Lee Jones 2020-07-01 14:10 ` Baolin Wang 2020-07-01 14:10 ` Baolin Wang 2020-06-29 12:32 ` [PATCH 5/5] mfd: axp20x-i2c: Do not define 'struct acpi_device_id' when !CONFIG_ACPI Lee Jones 2020-06-29 12:32 ` Lee Jones 2020-06-29 15:38 ` Chen-Yu Tsai 2020-06-29 15:38 ` Chen-Yu Tsai 2020-07-06 7:31 ` Lee Jones 2020-07-06 7:31 ` Lee Jones 2020-07-01 6:59 ` [PATCH v2] mfd: axp20x-i2c: Tell the compiler that ACPI functions may not be used Lee Jones 2020-07-01 6:59 ` Lee Jones 2020-07-01 8:38 ` Chen-Yu Tsai 2020-07-01 8:38 ` Chen-Yu Tsai
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