diff mbox series

drivers/staging/pi433: Change data type of bit_rate to be u32

Message ID 20221020181815.31245-1-gautammenghani201@gmail.com
State New
Headers
Series drivers/staging/pi433: Change data type of bit_rate to be u32 |

Commit Message

Gautam Menghani Oct. 20, 2022, 6:18 p.m. UTC 
  A TODO asks to convert the bit_rate variable to be a u32 so that bit 
rates up to 300kbps can be supported as per the spec.

Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
---
Please note that this patch is only compile tested.

 drivers/staging/pi433/TODO       | 2 --
 drivers/staging/pi433/pi433_if.h | 4 ++--
 drivers/staging/pi433/rf69.c     | 2 +-
 drivers/staging/pi433/rf69.h     | 2 +-
 4 files changed, 4 insertions(+), 6 deletions(-)

Comments

Paulo Miguel Almeida Oct. 20, 2022, 8:15 p.m. UTC | #1 
On Thu, Oct 20, 2022 at 11:48:15PM +0530, Gautam Menghani wrote:
> A TODO asks to convert the bit_rate variable to be a u32 so that bit 
> rates up to 300kbps can be supported as per the spec.
> 
Thanks for sending this patch. Comments added in-line.

> diff --git a/drivers/staging/pi433/pi433_if.h b/drivers/staging/pi433/pi433_if.h
> index 25ee0b77a32c..c958dcfa9f96 100644
> --- a/drivers/staging/pi433/pi433_if.h
> +++ b/drivers/staging/pi433/pi433_if.h
> @@ -51,7 +51,7 @@ enum option_on_off {
>  #define PI433_TX_CFG_IOCTL_NR	0
>  struct pi433_tx_cfg {
>  	__u32			frequency;
> -	__u16			bit_rate;
> +	__u32			bit_rate;
>  	__u32			dev_frequency;
>  	enum modulation		modulation;
>  	enum mod_shaping	mod_shaping;
> @@ -99,7 +99,7 @@ struct pi433_tx_cfg {
>  #define PI433_RX_CFG_IOCTL_NR	1
>  struct pi433_rx_cfg {
>  	__u32			frequency;
> -	__u16			bit_rate;
> +	__u32			bit_rate;
>  	__u32			dev_frequency;
>  
>  	enum modulation		modulation;

Cutting a long story short, you won't be able to change bit_rate's type before 
addressing the fact that both pi433_tx_cfg ans pi433_rx_cfg are part of the UAPI.

Usually there are 2 approaches that most people go for when talking about
changes in drivers:

1) Add changes in a backwards compatible way, so whether users are using the
        bitrate member as u32 or u64, it would simply work. But that leads to
        sometimes hard-to-read code.... but this is still a card up your sleeve.

        One suggestion given by Dan Carpenter was to leave the IOCTL impl alone
        and start a sysfs implementation. That way you could have a u64 bit_rate
        synthetic file.

        https://lore.kernel.org/all/20220119053410.GW1978@kadam/

2) Change the tools that make use of this driver at the same time as you change
        the UAPI. This can be tricky. There is a thread I started in the
        kernelnewbies mailing list on the subject which I think might be relevant
        for you to read.

        https://lore.kernel.org/all/YjHvLFSV06w%2FORgV@kroah.com/

Happy coding :-)

Paulo A.
Nam Cao Oct. 20, 2022, 8:22 p.m. UTC | #2 
On Thu, Oct 20, 2022 at 11:48:15PM +0530, Gautam Menghani wrote:
> A TODO asks to convert the bit_rate variable to be a u32 so that bit 
> rates up to 300kbps can be supported as per the spec.
> 
> Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
> ---
> Please note that this patch is only compile tested.
> 
>  drivers/staging/pi433/TODO       | 2 --
>  drivers/staging/pi433/pi433_if.h | 4 ++--
>  drivers/staging/pi433/rf69.c     | 2 +-
>  drivers/staging/pi433/rf69.h     | 2 +-
>  4 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/pi433/TODO b/drivers/staging/pi433/TODO
> index 5cf3fd99d521..8530bbe61d70 100644
> --- a/drivers/staging/pi433/TODO
> +++ b/drivers/staging/pi433/TODO
> @@ -1,5 +1,3 @@
>  * currently the code introduces new IOCTLs. I'm afraid this is a bad idea.
>    -> Replace this with another interface, hints are welcome!
>  * Some missing data (marked with ###) needs to be added in the documentation
> -* Change (struct pi433_tx_cfg)->bit_rate to be a u32 so that we can support
> -    bit rates up to 300kbps per the spec.
> diff --git a/drivers/staging/pi433/pi433_if.h b/drivers/staging/pi433/pi433_if.h
> index 25ee0b77a32c..c958dcfa9f96 100644
> --- a/drivers/staging/pi433/pi433_if.h
> +++ b/drivers/staging/pi433/pi433_if.h
> @@ -51,7 +51,7 @@ enum option_on_off {
>  #define PI433_TX_CFG_IOCTL_NR	0
>  struct pi433_tx_cfg {
>  	__u32			frequency;
> -	__u16			bit_rate;
> +	__u32			bit_rate;
>  	__u32			dev_frequency;
>  	enum modulation		modulation;
>  	enum mod_shaping	mod_shaping;
> @@ -99,7 +99,7 @@ struct pi433_tx_cfg {
>  #define PI433_RX_CFG_IOCTL_NR	1
>  struct pi433_rx_cfg {
>  	__u32			frequency;
> -	__u16			bit_rate;
> +	__u32			bit_rate;
>  	__u32			dev_frequency;
>  
>  	enum modulation		modulation;
> diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
> index 8c7fab6a46bb..7e754a3aef5f 100644
> --- a/drivers/staging/pi433/rf69.c
> +++ b/drivers/staging/pi433/rf69.c
> @@ -185,7 +185,7 @@ int rf69_set_modulation_shaping(struct spi_device *spi,
>  	}
>  }
>  
> -int rf69_set_bit_rate(struct spi_device *spi, u16 bit_rate)
> +int rf69_set_bit_rate(struct spi_device *spi, u32 bit_rate)
>  {
>  	int retval;
>  	u32 bit_rate_reg;
> diff --git a/drivers/staging/pi433/rf69.h b/drivers/staging/pi433/rf69.h
> index 78fa0b8bab8b..46a1fb2d5329 100644
> --- a/drivers/staging/pi433/rf69.h
> +++ b/drivers/staging/pi433/rf69.h
> @@ -24,7 +24,7 @@ int rf69_set_data_mode(struct spi_device *spi, u8 data_mode);
>  int rf69_set_modulation(struct spi_device *spi, enum modulation modulation);
>  int rf69_set_modulation_shaping(struct spi_device *spi,
>  				enum mod_shaping mod_shaping);
> -int rf69_set_bit_rate(struct spi_device *spi, u16 bit_rate);
> +int rf69_set_bit_rate(struct spi_device *spi, u32 bit_rate);
>  int rf69_set_deviation(struct spi_device *spi, u32 deviation);
>  int rf69_set_frequency(struct spi_device *spi, u32 frequency);
>  int rf69_enable_amplifier(struct spi_device *spi, u8 amplifier_mask);
> -- 
> 2.34.1
>

I sent (almost) the exact same patch a while ago. I received a reply
saying that doing this is not possible. That conversation can still be
found here:
https://lore.kernel.org/linux-staging/20220315180820.7393-1-cvn249@gmail.com/t/#u

Best regards,
Nam
diff mbox series

Patch

diff --git a/drivers/staging/pi433/TODO b/drivers/staging/pi433/TODO
index 5cf3fd99d521..8530bbe61d70 100644
--- a/drivers/staging/pi433/TODO
+++ b/drivers/staging/pi433/TODO
@@ -1,5 +1,3 @@ 
 * currently the code introduces new IOCTLs. I'm afraid this is a bad idea.
   -> Replace this with another interface, hints are welcome!
 * Some missing data (marked with ###) needs to be added in the documentation
-* Change (struct pi433_tx_cfg)->bit_rate to be a u32 so that we can support
-    bit rates up to 300kbps per the spec.
diff --git a/drivers/staging/pi433/pi433_if.h b/drivers/staging/pi433/pi433_if.h
index 25ee0b77a32c..c958dcfa9f96 100644
--- a/drivers/staging/pi433/pi433_if.h
+++ b/drivers/staging/pi433/pi433_if.h
@@ -51,7 +51,7 @@  enum option_on_off {
 #define PI433_TX_CFG_IOCTL_NR	0
 struct pi433_tx_cfg {
 	__u32			frequency;
-	__u16			bit_rate;
+	__u32			bit_rate;
 	__u32			dev_frequency;
 	enum modulation		modulation;
 	enum mod_shaping	mod_shaping;
@@ -99,7 +99,7 @@  struct pi433_tx_cfg {
 #define PI433_RX_CFG_IOCTL_NR	1
 struct pi433_rx_cfg {
 	__u32			frequency;
-	__u16			bit_rate;
+	__u32			bit_rate;
 	__u32			dev_frequency;
 
 	enum modulation		modulation;
diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
index 8c7fab6a46bb..7e754a3aef5f 100644
--- a/drivers/staging/pi433/rf69.c
+++ b/drivers/staging/pi433/rf69.c
@@ -185,7 +185,7 @@  int rf69_set_modulation_shaping(struct spi_device *spi,
 	}
 }
 
-int rf69_set_bit_rate(struct spi_device *spi, u16 bit_rate)
+int rf69_set_bit_rate(struct spi_device *spi, u32 bit_rate)
 {
 	int retval;
 	u32 bit_rate_reg;
diff --git a/drivers/staging/pi433/rf69.h b/drivers/staging/pi433/rf69.h
index 78fa0b8bab8b..46a1fb2d5329 100644
--- a/drivers/staging/pi433/rf69.h
+++ b/drivers/staging/pi433/rf69.h
@@ -24,7 +24,7 @@  int rf69_set_data_mode(struct spi_device *spi, u8 data_mode);
 int rf69_set_modulation(struct spi_device *spi, enum modulation modulation);
 int rf69_set_modulation_shaping(struct spi_device *spi,
 				enum mod_shaping mod_shaping);
-int rf69_set_bit_rate(struct spi_device *spi, u16 bit_rate);
+int rf69_set_bit_rate(struct spi_device *spi, u32 bit_rate);
 int rf69_set_deviation(struct spi_device *spi, u32 deviation);
 int rf69_set_frequency(struct spi_device *spi, u32 frequency);
 int rf69_enable_amplifier(struct spi_device *spi, u8 amplifier_mask);