netdev - Re: [PATCH v14 01/22] cxl: add type2 device basic support

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Message-ID: <aBv59PLYPD4MeDrE@aschofie-mobl2.lan>
Date: Wed, 7 May 2025 17:25:24 -0700
From: Alison Schofield <alison.schofield@...el.com>
To: <alejandro.lucero-palau@....com>
CC: <linux-cxl@...r.kernel.org>, <netdev@...r.kernel.org>,
	<dan.j.williams@...el.com>, <edward.cree@....com>, <davem@...emloft.net>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <edumazet@...gle.com>,
	<dave.jiang@...el.com>, Alejandro Lucero <alucerop@....com>, Jonathan Cameron
	<Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v14 01/22] cxl: add type2 device basic support

On Thu, Apr 17, 2025 at 10:29:04PM +0100, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Differentiate CXL memory expanders (type 3) from CXL device accelerators
> (type 2) with a new function for initializing cxl_dev_state and a macro
> for helping accel drivers to embed cxl_dev_state inside a private
> struct.
> 
> Move structs to include/cxl as the size of the accel driver private
> struct embedding cxl_dev_state needs to know the size of this struct.
> 
> Use same new initialization with the type3 pci driver.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>

snip


> +
> +struct cxl_dev_state *_cxl_dev_state_create(struct device *dev,
> +					    enum cxl_devtype type, u64 serial,
> +					    u16 dvsec, size_t size,
> +					    bool has_mbox);
> +
> +#define cxl_dev_state_create(parent, type, serial, dvsec, drv_struct, member, mbox)	\
> +	({										\
> +		static_assert(__same_type(struct cxl_dev_state,				\
> +			      ((drv_struct *)NULL)->member));				\
> +		static_assert(offsetof(drv_struct, member) == 0);			\
> +		(drv_struct *)_cxl_dev_state_create(parent, type, serial, dvsec,	\
> +						      sizeof(drv_struct), mbox);	\
> +	})

I spent a bit of time unravelling this macro and came to understand that
as a macro it can enforce compile time correctness, and that is all good.
However, a comment would be appreciated.
Perhaps: Safely create and cast a cxl dev state embedded in a driver
specific struct. Introduced for Type 2 driver support.




>