linux-kernel - Re: [PATCH net-next 3/7] net: phy: introduce phy_read_mmd_poll

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Date:   Thu, 19 Mar 2020 17:56:39 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Dejin Zheng <zhengdejin5@...il.com>, andrew@...n.ch,
        f.fainelli@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        tglx@...utronix.de, broonie@...nel.org, corbet@....net,
        mchehab+samsung@...nel.org, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/7] net: phy: introduce
 phy_read_mmd_poll_timeout macro

On 19.03.2020 17:39, Dejin Zheng wrote:
> it is sometimes necessary to poll a phy register by phy_read_mmd()
> function until its value satisfies some condition. introduce
> phy_read_mmd_poll_timeout() macros that do this.
> 
> Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>
> ---
>  include/linux/phy.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 36d9dea04016..a30e9008647f 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -24,6 +24,7 @@
>  #include <linux/mod_devicetable.h>
>  #include <linux/u64_stats_sync.h>
>  #include <linux/irqreturn.h>
> +#include <linux/iopoll.h>
>  
>  #include <linux/atomic.h>
>  
> @@ -784,6 +785,9 @@ static inline int __phy_modify_changed(struct phy_device *phydev, u32 regnum,
>   */
>  int phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum);
>  
> +#define phy_read_mmd_poll_timeout(val, cond, sleep_us, timeout_us, args...) \
> +	read_poll_timeout(phy_read_mmd, val, cond, sleep_us, timeout_us, args)
> +
>  /**
>   * __phy_read_mmd - Convenience function for reading a register
>   * from an MMD on a given PHY.
> 
I'm not fully convinced. Usage of the new macro with its lots of
parameters makes the code quite hard to read. Therefore I'm also
not a big fan of readx_poll_timeout.

Even though I didn't invent it, I prefer the way DECLARE_RTL_COND
is used in the r8169 driver. The resulting code is much better
to read, and in case of a timeout a helpful warning is printed
automatically.