Re: [PATCH][next] mtd: rawnand: Replace one-element array with flexible-array member

Jann Horn
2020-09-30T21:12:08Z

On Wed, Sep 30, 2020 at 11:02 PM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].

But this is not such a case, right? Isn't this a true fixed-size
array? It sounds like you're just changing it because it
pattern-matched on "array of length 1 at the end of a struct".

> Refactor the code according to the use of a flexible-array member
> instead of a one-element array. Also, make use of the struct_size()
> helper to calculate the size of the allocation for _nand_. In order
> to keep the code as maintainable as possible and to keep _cs_ as an
> array, add a new macro CS_N to aid in the allocation size calculation,
> in case there is a need for more Chip Select IDs in the future. In the
> meantime, the macro is set to 1. This also avoids having to use a magic
> number '1' as the last argument for struct_size().
[...]
> diff --git a/drivers/mtd/nand/raw/tegra_nand.c b/drivers/mtd/nand/raw/tegra_nand.c
[...]
> +/* Number of Chip Selects. Currently, only one. */
> +#define CS_N 1
> +
> struct tegra_nand_controller {
> struct nand_controller controller;
> struct device *dev;
> @@ -183,7 +186,7 @@ struct tegra_nand_chip {
> u32 config;
> u32 config_ecc;
> u32 bch_config;
> - int cs[1];
> + int cs[];
> }; …