Re: [PATCHv3] ARM: omap2: simplify allocation for omap_device

[Kevin Hilman <khilman@baylibre.com>]

Rosen Penev <rosenp@gmail.com> writes:

> Use a flexible array member (FAM) to combine hwmods array allocation
> with the omap_device structure. This reduces the number of allocations
> from two separate calls (one for the device, one for the array) to a
> single allocation, improving efficiency and reducing memory fragmentation.
>
> The FAM approach also enables bounds checking through __counted_by(),
> which provides runtime verification that array accesses stay within
> the allocated size. This improves security and helps catch bugs during
> development.
>
> Simplify error handling by removing the unnecessary multi-label goto
> pattern. The new code is more straightforward: allocate, verify, copy
> data, and either return success or error immediately.
>
> Also removes the now-redundant kfree(od->hwmods) in omap_device_delete()
> since the hwmods array is now embedded in the structure rather than
> separately allocated.
>
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

Thanks for this cleanup.

> ---
>  v3: add a verbose description explaining why. Powered by Claude Sonnet
>  4.5.
>  v2: remove kfree and fix compilation.
>  arch/arm/mach-omap2/omap_device.c | 29 ++++++++++-------------------
>  arch/arm/mach-omap2/omap_device.h |  4 ++--
>  2 files changed, 12 insertions(+), 21 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/omap_device.c b/arch/arm/mach-omap2/omap_device.c
> index 79db4c49ffc9..77a75b0b9ae6 100644
> --- a/arch/arm/mach-omap2/omap_device.c
> +++ b/arch/arm/mach-omap2/omap_device.c
> @@ -307,35 +307,27 @@ static struct omap_device *omap_device_alloc(struct platform_device *pdev,
>  	int ret = -ENOMEM;
>  	struct omap_device *od;
>  	int i;
> -	struct omap_hwmod **hwmods;
> +	struct omap_hwmod *hwmod;
>
> -	od = kzalloc_obj(struct omap_device);
> -	if (!od)
> -		goto oda_exit1;
> +	od = kzalloc_flex(*od, hwmods, oh_cnt);
> +	if (!od) {
> +		dev_err(&pdev->dev, "omap_device: build failed (%d)\n", ret);
> +		return ERR_PTR(ret);
> +	}
>
>  	od->hwmods_cnt = oh_cnt;

minor nit: isn't this assignment redundant now, as kalloc_flex() should
assign the count?

> +	memcpy(od->hwmods, ohs, oh_cnt * sizeof(*od->hwmods));
>

> -	hwmods = kmemdup_array(ohs, oh_cnt, sizeof(*hwmods), GFP_KERNEL);
> -	if (!hwmods)
> -		goto oda_exit2;
> -
> -	od->hwmods = hwmods;
>  	od->pdev = pdev;
>  	pdev->archdata.od = od;
>
>  	for (i = 0; i < oh_cnt; i++) {
> -		hwmods[i]->od = od;
> -		_add_hwmod_clocks_clkdev(od, hwmods[i]);
> +		hwmod = od->hwmods[i];
> +		hwmod->od = od;
> +		_add_hwmod_clocks_clkdev(od, hwmod);
>  	}
>
>  	return od;
> -
> -oda_exit2:
> -	kfree(od);
> -oda_exit1:
> -	dev_err(&pdev->dev, "omap_device: build failed (%d)\n", ret);
> -
> -	return ERR_PTR(ret);
>  }

Kevin