Subject: Re: [PATCH 19/36] Bluetooth: SMP: Use new AES library API

From: David Laight <[email-masked]>
Date: Mon, 5 Jan 2026 19:05:03 +0000

On Mon, 5 Jan 2026 15:40:22 +0000
Andrew Cooper <[email-masked]> wrote:

> >  	/* Most significant octet of plaintextData corresponds to data[0] */
> >  	swap_buf(r, data, 16);
> >  
> > - aes_encrypt(&ctx, data, data); + aes_encrypt_new(&aes, data, data);  
> 
> One thing you might want to consider, which reduces the churn in the series.
> 
> You can use _Generic() to do type-based dispatch on the first pointer. 
> Something like this:
> 
> void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in);
> void aes_encrypt_new(aes_encrypt_arg key, u8 out[at_least AES_BLOCK_SIZE],
>              const u8 in[at_least AES_BLOCK_SIZE]);
> 
> #define aes_encrypt(ctx, out, in)                                       \
>     _Generic(ctx,                                                       \
>              const struct crypto_aes_ctx *: aes_encrypt(ctx, out, in),  \
>              aes_encrypt_arg: aes_encrypt_new(ctx, out, in))
> 
> 
> i.e. it keeps the _new()-ism in a single header, without needing to
> change the drivers a second time.

You'll need to cast the 'ctx' argument in both calls.
All the code in an _Generic() must compile cleanly in all the cases.
(Totally annoying....)

	David

> ~Andrew