netdev - Re: [PATCH v4 02/10] fwctl: Basic ioctl dispatch for the character device

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Message-ID: <b25e45e0-7c37-4e93-8372-e3fbfc3b7903@intel.com>
Date: Thu, 13 Feb 2025 13:42:44 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: Andy Gospodarek <andrew.gospodarek@...adcom.com>, Aron Silverton
	<aron.silverton@...cle.com>, Dan Williams <dan.j.williams@...el.com>, "Daniel
 Vetter" <daniel.vetter@...ll.ch>, Dave Jiang <dave.jiang@...el.com>, "David
 Ahern" <dsahern@...nel.org>, Andy Gospodarek <gospo@...adcom.com>, "Christoph
 Hellwig" <hch@...radead.org>, Itay Avraham <itayavr@...dia.com>, Jiri Pirko
	<jiri@...dia.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Leonid Bloch <lbloch@...dia.com>, Leon
 Romanovsky <leonro@...dia.com>, <linux-cxl@...r.kernel.org>,
	<linux-rdma@...r.kernel.org>, <netdev@...r.kernel.org>, Saeed Mahameed
	<saeedm@...dia.com>, "Nelson, Shannon" <shannon.nelson@....com>
Subject: Re: [PATCH v4 02/10] fwctl: Basic ioctl dispatch for the character
 device

On 2/7/25 01:13, Jason Gunthorpe wrote:
> Each file descriptor gets a chunk of per-FD driver specific context that
> allows the driver to attach a device specific struct to. The core code
> takes care of the memory lifetime for this structure.
> 
> The ioctl dispatch and design is based on what was built for iommufd. The
> ioctls have a struct which has a combined in/out behavior with a typical
> 'zero pad' scheme for future extension and backwards compatibility.
> 
> Like iommufd some shared logic does most of the ioctl marshalling and
> compatibility work and tables diatches to some function pointers for
> each unique iotcl.
> 
> This approach has proven to work quite well in the iommufd and rdma
> subsystems.
> 
> Allocate an ioctl number space for the subsystem.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>


> diff --git a/drivers/fwctl/main.c b/drivers/fwctl/main.c
> index 34946bdc3bf3d7..d561deaf2b86d8 100644
> --- a/drivers/fwctl/main.c
> +++ b/drivers/fwctl/main.c
> @@ -10,6 +10,8 @@
>   #include <linux/module.h>
>   #include <linux/slab.h>
>   
> +#include <uapi/fwctl/fwctl.h>
> +
>   enum {
>   	FWCTL_MAX_DEVICES = 4096,
>   };
> @@ -18,20 +20,128 @@ static_assert(FWCTL_MAX_DEVICES < (1U << MINORBITS));
>   static dev_t fwctl_dev;
>   static DEFINE_IDA(fwctl_ida);
>   
> +struct fwctl_ucmd {
> +	struct fwctl_uctx *uctx;
> +	void __user *ubuffer;
> +	void *cmd;
> +	u32 user_size;
> +};
> +
> +/* On stack memory for the ioctl structs */
> +union ucmd_buffer {

for most names you follow the usual prefixing rules, would be good
to do for all