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Date: Sun, 17 Dec 2023 13:24:47 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Joe Perches <joe@...ches.com>
Cc: Justin Stitt <justinstitt@...gle.com>, Lars-Peter Clausen
<lars@...afoo.de>, Stephen Boyd <swboyd@...omium.org>,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] iio: sx9324: avoid copying property strings
On Mon, 11 Dec 2023 22:30:12 -0800
Joe Perches <joe@...ches.com> wrote:
> On Tue, 2023-12-12 at 00:42 +0000, Justin Stitt wrote:
> > We're doing some needless string copies when trying to assign the proper
> > `prop` string. We can make `prop` a const char* and simply assign to
> > string literals.
>
> trivia:
>
> I would have updated it like this moving the
> various declarations into the case blocks
> where they are used and removing a few unused
> #defines
I'd definitely like to see those defines gone.
Arguably an unrelated change as I guess they are left from a previous refactor
of this code.
Why prop to type renaming? It's getting passed into calls where the parameter
is propname so I'd understand renaming to that, but type just seems a bit random
to me. I do wonder if we are better off having some long lines and getting rid
of the property naming local variables completely by just duplicating
the device_property_read_u32() call and passing them in directly.
Moving declarations more locally is a nice to have but I'll leave that up to Justin.
Anyhow, both solutions look much better than the original so I'm fine either way
(subject to responses to Stephen's review)
>
> ---
> drivers/iio/proximity/sx9324.c | 69 +++++++++++++++++++++++++-----------------
> 1 file changed, 41 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
> index ac2ed2da21ccc..c50c1108a69cc 100644
> --- a/drivers/iio/proximity/sx9324.c
> +++ b/drivers/iio/proximity/sx9324.c
> @@ -877,17 +877,8 @@ static const struct sx_common_reg_default *
> sx9324_get_default_reg(struct device *dev, int idx,
> struct sx_common_reg_default *reg_def)
> {
> - static const char * const sx9324_rints[] = { "lowest", "low", "high",
> - "highest" };
> - static const char * const sx9324_csidle[] = { "hi-z", "hi-z", "gnd",
> - "vdd" };
> -#define SX9324_PIN_DEF "semtech,ph0-pin"
> -#define SX9324_RESOLUTION_DEF "semtech,ph01-resolution"
> -#define SX9324_PROXRAW_DEF "semtech,ph01-proxraw-strength"
> - unsigned int pin_defs[SX9324_NUM_PINS];
> - char prop[] = SX9324_PROXRAW_DEF;
> - u32 start = 0, raw = 0, pos = 0;
> - int ret, count, ph, pin;
> + u32 raw = 0;
> + int ret;
>
> memcpy(reg_def, &sx9324_default_regs[idx], sizeof(*reg_def));
>
> @@ -896,7 +887,13 @@ sx9324_get_default_reg(struct device *dev, int idx,
> case SX9324_REG_AFE_PH0:
> case SX9324_REG_AFE_PH1:
> case SX9324_REG_AFE_PH2:
> - case SX9324_REG_AFE_PH3:
> + case SX9324_REG_AFE_PH3: {
> + unsigned int pin_defs[SX9324_NUM_PINS];
> + int count;
> + int pin;
> + int ph;
> + char prop[32];
> +
> ph = reg_def->reg - SX9324_REG_AFE_PH0;
> snprintf(prop, ARRAY_SIZE(prop), "semtech,ph%d-pin", ph);
>
> @@ -913,7 +910,15 @@ sx9324_get_default_reg(struct device *dev, int idx,
> SX9324_REG_AFE_PH0_PIN_MASK(pin);
> reg_def->def = raw;
> break;
> - case SX9324_REG_AFE_CTRL0:
> + }
> + case SX9324_REG_AFE_CTRL0: {
> + static const char * const sx9324_csidle[] = {
> + "hi-z", "hi-z", "gnd", "vdd"
> + };
> + static const char * const sx9324_rints[] = {
> + "lowest", "low", "high", "highest"
> + };
> +
> ret = device_property_match_property_string(dev, "semtech,cs-idle-sleep",
> sx9324_csidle,
> ARRAY_SIZE(sx9324_csidle));
> @@ -930,16 +935,17 @@ sx9324_get_default_reg(struct device *dev, int idx,
> reg_def->def |= ret << SX9324_REG_AFE_CTRL0_RINT_SHIFT;
> }
> break;
> + }
> case SX9324_REG_AFE_CTRL4:
> - case SX9324_REG_AFE_CTRL7:
> + case SX9324_REG_AFE_CTRL7: {
> + const char *type;
> +
> if (reg_def->reg == SX9324_REG_AFE_CTRL4)
> - strncpy(prop, "semtech,ph01-resolution",
> - ARRAY_SIZE(prop));
> + type = "semtech,ph01-resolution";
> else
> - strncpy(prop, "semtech,ph23-resolution",
> - ARRAY_SIZE(prop));
> + type = "semtech,ph23-resolution";
>
> - ret = device_property_read_u32(dev, prop, &raw);
> + ret = device_property_read_u32(dev, type, &raw);
> if (ret)
> break;
>
> @@ -949,6 +955,7 @@ sx9324_get_default_reg(struct device *dev, int idx,
> reg_def->def |= FIELD_PREP(SX9324_REG_AFE_CTRL4_RESOLUTION_MASK,
> raw);
> break;
> + }
> case SX9324_REG_AFE_CTRL8:
> ret = device_property_read_u32(dev,
> "semtech,input-precharge-resistor-ohms",
> @@ -982,17 +989,21 @@ sx9324_get_default_reg(struct device *dev, int idx,
> 6 + raw * (raw + 3) / 2);
> break;
>
> - case SX9324_REG_ADV_CTRL5:
> + case SX9324_REG_ADV_CTRL5: {
> + u32 start = 0;
> +
> ret = device_property_read_u32(dev, "semtech,startup-sensor",
> &start);
> if (ret)
> break;
> -
> reg_def->def &= ~SX9324_REG_ADV_CTRL5_STARTUPSENS_MASK;
> reg_def->def |= FIELD_PREP(SX9324_REG_ADV_CTRL5_STARTUPSENS_MASK,
> start);
> break;
> - case SX9324_REG_PROX_CTRL4:
> + }
> + case SX9324_REG_PROX_CTRL4: {
> + u32 pos = 0;
> +
> ret = device_property_read_u32(dev, "semtech,avg-pos-strength",
> &pos);
> if (ret)
> @@ -1005,15 +1016,16 @@ sx9324_get_default_reg(struct device *dev, int idx,
> reg_def->def |= FIELD_PREP(SX9324_REG_PROX_CTRL4_AVGPOSFILT_MASK,
> raw);
> break;
> + }
> case SX9324_REG_PROX_CTRL0:
> - case SX9324_REG_PROX_CTRL1:
> + case SX9324_REG_PROX_CTRL1: {
> + const char *type;
> +
> if (reg_def->reg == SX9324_REG_PROX_CTRL0)
> - strncpy(prop, "semtech,ph01-proxraw-strength",
> - ARRAY_SIZE(prop));
> + type = "semtech,ph01-proxraw-strength";
> else
> - strncpy(prop, "semtech,ph23-proxraw-strength",
> - ARRAY_SIZE(prop));
> - ret = device_property_read_u32(dev, prop, &raw);
> + type = "semtech,ph23-proxraw-strength";
> + ret = device_property_read_u32(dev, type, &raw);
> if (ret)
> break;
>
> @@ -1022,6 +1034,7 @@ sx9324_get_default_reg(struct device *dev, int idx,
> raw);
> break;
> }
> + }
> return reg_def;
> }
>
>
>
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