netdev - Re: [PATCH net-next 1/2] net: dsa: microchip: properly support platform

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Date: Wed, 6 Dec 2023 16:42:52 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Daniel Danzberger <dd@...edd.com>
Cc: woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com,
	f.fainelli@...il.com, olteanv@...il.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net-next 1/2] net: dsa: microchip: properly support
 platform_data probing

On Tue, Dec 05, 2023 at 05:42:30PM +0100, Daniel Danzberger wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> The ksz driver has bits and pieces of platform_data probing support, but
> it doesn't work.
> 
> The conventional thing to do is to have an encapsulating structure for
> struct dsa_chip_data that gets put into dev->platform_data. This driver
> expects a struct ksz_platform_data, but that doesn't contain a struct
> dsa_chip_data as first element, which will obviously not work with
> dsa_switch_probe() -> dsa_switch_parse().
> 
> Pointing dev->platform_data to a struct dsa_chip_data directly is in
> principle possible, but that doesn't work either. The driver has
> ksz_switch_detect() to read the device ID from hardware, followed by
> ksz_check_device_id() to compare it against a predetermined expected
> value. This protects against early errors in the SPI/I2C communication.
> With platform_data, the mechanism in ksz_check_device_id() doesn't work
> and even leads to NULL pointer dereferences, since of_device_get_match_data()
> doesn't work in that probe path.
> 
> So obviously, the platform_data support is actually missing, and the
> existing handling of struct ksz_platform_data is bogus. Complete the
> support by adding a struct dsa_chip_data as first element, and fixing up
> ksz_check_device_id() to pick up the platform_data instead of the
> unavailable of_device_get_match_data().
> 
> The early dev->chip_id assignment from ksz_switch_register() is also
> bogus, because ksz_switch_detect() sets it to an initial value. So
> remove it.
> 
> Also, ksz_platform_data :: enabled_ports isn't used anywhere, delete it.
> 
> Link: https://lore.kernel.org/netdev/20231204154315.3906267-1-dd@embedd.com/
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Signed-off-by: Daniel Danzberger <dd@...edd.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew