Re: [PATCH v3] iio: sx9324: avoid copying property strings
On Sun, 2023-12-17 at 13:24 +, Jonathan Cameron wrote: > On Mon, 11 Dec 2023 22:30:12 -0800 > Joe Perches wrote: > > > On Tue, 2023-12-12 at 00:42 +, 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? random, no specific need, though I prefer not reusing identifiers with different types in separate local scopes. > 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. maybe, give it a try and see what you think.
Re: [PATCH v3] iio: sx9324: avoid copying property strings
On Mon, 11 Dec 2023 22:30:12 -0800
Joe Perches wrote:
> On Tue, 2023-12-12 at 00:42 +, 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:
> r
Re: [PATCH v3] iio: sx9324: avoid copying property strings
Quoting Justin Stitt (2023-12-11 16:42:52)
> diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
> index 438f9c9aba6e..e3bc30b57b19 100644
> --- a/drivers/iio/proximity/sx9324.c
> +++ b/drivers/iio/proximity/sx9324.c
> @@ -873,6 +873,32 @@ static int sx9324_init_compensation(struct iio_dev
> *indio_dev)
> 2, 200);
> }
>
> +static u32 sx9324_parse_phase_prop(struct device *dev,
return u8? because that's the type of struct sx_common_reg_default::def.
> + struct sx_common_reg_default *reg_def,
> + int idx, const char *prop)
> +{
> + unsigned int pin_defs[SX9324_NUM_PINS];
> + int count, ret, pin;
> + u8 default_def;
> + u32 raw = 0;
> +
> + default_def = sx9324_default_regs[idx].def;
Do we need to do this? Isn't this reg_def->def?
> +
> + count = device_property_count_u32(dev, prop);
> + if (count != ARRAY_SIZE(pin_defs))
> + return default_def;
return reg_def->def?
> + ret = device_property_read_u32_array(dev, prop, pin_defs,
> +ARRAY_SIZE(pin_defs));
> + if (ret)
> + return default_def;
return reg_def->def?
> +
> + for (pin = 0; pin < SX9324_NUM_PINS; pin++)
> + raw |= (pin_defs[pin] << (2 * pin)) &
> + SX9324_REG_AFE_PH0_PIN_MASK(pin);
> +
> + return raw;
> +}
> +
> static const struct sx_common_reg_default *
> sx9324_get_default_reg(struct device *dev, int idx,
>struct sx_common_reg_default *reg_def)
> @@ -884,35 +910,30 @@ sx9324_get_default_reg(struct device *dev, int idx,
> #define SX9324_PIN_DEF "semtech,ph0-pin"
> #define SX9324_RESOLUTION_DEF "semtech,ph01-resolution"
> #define SX9324_PROXRAW_DEF "semtech,ph01-proxraw-strength"
Can you send a followup to remove these defines?
> - unsigned int pin_defs[SX9324_NUM_PINS];
> - char prop[] = SX9324_PROXRAW_DEF;
> + const char *prop = SX9324_PROXRAW_DEF;
This can be left unassigned now, right?
> u32 start = 0, raw = 0, pos = 0;
> - int ret, count, ph, pin;
> const char *res;
> + int ret;
Re: [PATCH v3] iio: sx9324: avoid copying property strings
On Tue, Dec 12, 2023 at 12:42:52AM +, 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. > > For the case where a format string is used, let's extract the parsing > logic out into sx9324_parse_phase_prop(). We no longer need to create > copies or allocate new memory. > > sx9324_parse_phase_prop() will simply return the default def value if it > fails. > > This also cleans up some deprecated strncpy() uses [1]. > > Link: > https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings > [1] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt Yeah, I like this approach. Totally removes the string copying and creates a helper that does the "heavy lifting". :) Reviewed-by: Kees Cook -- Kees Cook
Re: [PATCH v3] iio: sx9324: avoid copying property strings
On Tue, 2023-12-12 at 00:42 +, 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
---
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_
[PATCH v3] iio: sx9324: avoid copying property strings
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.
For the case where a format string is used, let's extract the parsing
logic out into sx9324_parse_phase_prop(). We no longer need to create
copies or allocate new memory.
sx9324_parse_phase_prop() will simply return the default def value if it
fails.
This also cleans up some deprecated strncpy() uses [1].
Link:
https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
[1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt
---
Changes in v3:
- extract logic into sx9324_parse_phase_prop() and use string literals
(thanks Stephen)
- rebase onto mainline bee0e7762ad2c602
- Link to v2:
https://lore.kernel.org/r/20231026-strncpy-drivers-iio-proximity-sx9324-c-v2-1-cee6e5db7...@google.com
Changes in v2:
- make prop a const char* and do simple assignments (thanks Jonathan)
- rebase onto 3a568e3a961ba330
- Link to v1:
https://lore.kernel.org/r/20230921-strncpy-drivers-iio-proximity-sx9324-c-v1-1-4e8d28fd1...@google.com
---
---
drivers/iio/proximity/sx9324.c | 69 ++
1 file changed, 43 insertions(+), 26 deletions(-)
diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
index 438f9c9aba6e..e3bc30b57b19 100644
--- a/drivers/iio/proximity/sx9324.c
+++ b/drivers/iio/proximity/sx9324.c
@@ -873,6 +873,32 @@ static int sx9324_init_compensation(struct iio_dev
*indio_dev)
2, 200);
}
+static u32 sx9324_parse_phase_prop(struct device *dev,
+ struct sx_common_reg_default *reg_def,
+ int idx, const char *prop)
+{
+ unsigned int pin_defs[SX9324_NUM_PINS];
+ int count, ret, pin;
+ u8 default_def;
+ u32 raw = 0;
+
+ default_def = sx9324_default_regs[idx].def;
+
+ count = device_property_count_u32(dev, prop);
+ if (count != ARRAY_SIZE(pin_defs))
+ return default_def;
+ ret = device_property_read_u32_array(dev, prop, pin_defs,
+ARRAY_SIZE(pin_defs));
+ if (ret)
+ return default_def;
+
+ for (pin = 0; pin < SX9324_NUM_PINS; pin++)
+ raw |= (pin_defs[pin] << (2 * pin)) &
+ SX9324_REG_AFE_PH0_PIN_MASK(pin);
+
+ return raw;
+}
+
static const struct sx_common_reg_default *
sx9324_get_default_reg(struct device *dev, int idx,
struct sx_common_reg_default *reg_def)
@@ -884,35 +910,30 @@ sx9324_get_default_reg(struct device *dev, int idx,
#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;
+ const char *prop = SX9324_PROXRAW_DEF;
u32 start = 0, raw = 0, pos = 0;
- int ret, count, ph, pin;
const char *res;
+ int ret;
memcpy(reg_def, &sx9324_default_regs[idx], sizeof(*reg_def));
sx_common_get_raw_register_config(dev, reg_def);
switch (reg_def->reg) {
case SX9324_REG_AFE_PH0:
+ reg_def->def = sx9324_parse_phase_prop(dev, reg_def, idx,
+ "semtech,ph0-pin");
+ break;
case SX9324_REG_AFE_PH1:
+ reg_def->def = sx9324_parse_phase_prop(dev, reg_def, idx,
+ "semtech,ph1-pin");
+ break;
case SX9324_REG_AFE_PH2:
+ reg_def->def = sx9324_parse_phase_prop(dev, reg_def, idx,
+ "semtech,ph2-pin");
+ break;
case SX9324_REG_AFE_PH3:
- ph = reg_def->reg - SX9324_REG_AFE_PH0;
- snprintf(prop, ARRAY_SIZE(prop), "semtech,ph%d-pin", ph);
-
- count = device_property_count_u32(dev, prop);
- if (count != ARRAY_SIZE(pin_defs))
- break;
- ret = device_property_read_u32_array(dev, prop, pin_defs,
-ARRAY_SIZE(pin_defs));
- if (ret)
- break;
-
- for (pin = 0; pin < SX9324_NUM_PINS; pin++)
- raw |= (pin_defs[pin] << (2 * pin)) &
- SX9324_REG_AFE_PH0_PIN_MASK(pin);
- reg_def->def = raw;
+ reg_def->def = sx9324_parse_phase_prop(dev, reg_def, idx,
+ "semtech,ph3-pin");
break;
case SX9324_REG_AFE_CTRL0:
ret = device_property_read_string(dev,
@@ -937,11 +958,9
