linux-kernel - Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

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Message-ID: <CAHk-=wgH0oETG1eY9WS79aKrPqYZZzfOYxjtgmyr7jH52c8vsg@mail.gmail.com>
Date: Sun, 28 Jul 2024 12:55:06 -0700
From: Linus Torvalds <torvalds@...uxfoundation.org>
To: David Laight <David.Laight@...lab.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, 
	"Matthew Wilcox (Oracle)" <willy@...radead.org>, Christoph Hellwig <hch@...radead.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, Arnd Bergmann <arnd@...nel.org>, 
	"Jason@...c4.com" <Jason@...c4.com>, "pedro.falcato@...il.com" <pedro.falcato@...il.com>, 
	Mateusz Guzik <mjguzik@...il.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

On Sun, 28 Jul 2024 at 11:12, David Laight <David.Laight@...lab.com> wrote:
>
> Although min_t(type,x,y) should just be
>         type __x = x;
>         type __y = y;
>         __x < __y ? __x : __y;
> Absolutely no point doing anything else.

I tried it. Doesn't quite work:

  net/ipv4/proc.c: In function ‘snmp_seq_show_tcp_udp’:
  net/ipv4/proc.c:414:9: error: ISO C90 forbids variable length array
‘buff’ [-Werror=vla]
    414 |         unsigned long buff[TCPUDP_MIB_MAX];
        |         ^~~~~~~~

(and same issue repeated twice for IPv6).

Similar case here:

  drivers/gpu/drm/drm_color_mgmt.c: In function
‘drm_plane_create_color_properties’:
  drivers/gpu/drm/drm_color_mgmt.c:535:16: error: ISO C90 forbids
variable length array ‘enum_list’ [-Werror=vla]
    535 |         struct drm_prop_enum_list enum_list[max_t(int,
DRM_COLOR_ENCODING_MAX,
        |                ^~~~~~~~~~~~~~~~~~

and

  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c: In function
‘stmmac_dma_interrupt’:
  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:2915:9: error: ISO
C90 forbids variable length array ‘status’ [-Werror=vla]
   2915 |         int status[max_t(u32, MTL_MAX_TX_QUEUES, MTL_MAX_RX_QUEUES)];
        |         ^~~

and several cases in drivers/md/dm-integrity.c.

I guess all of these could just be made to use MIN_T()/MAX_T instead.
We're not talking hundreds of cases, it seems to be just a small
handful.

Let me go check.

               Linus