From: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
To: Gautam Menghani <gautammenghani201@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-staging@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drivers/staging/pi433: Change data type of bit_rate to be u32
Date: Fri, 21 Oct 2022 09:15:53 +1300 [thread overview]
Message-ID: <Y1GseU1Z+CCHJs9I@mail.google.com> (raw)
In-Reply-To: <20221020181815.31245-1-gautammenghani201@gmail.com>
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.
next prev parent reply other threads:[~2022-10-20 20:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-20 18:18 [PATCH] drivers/staging/pi433: Change data type of bit_rate to be u32 Gautam Menghani
2022-10-20 20:15 ` Paulo Miguel Almeida [this message]
2022-10-20 20:22 ` Nam Cao
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