Re: [PATCH v6 02/11] printk: Use struct console for suppression and extended console state

[John Ogness]

On 2024-10-28, Chris Down <chris@xxxxxxxxxxxxxx> wrote:
> In preparation for supporting per-console loglevels, modify
> printk_get_next_message() to accept the console itself instead of
> individual arguments that mimic its fields.

Sorry, this is not allowed. printk_get_next_message() was created
specifically to locklessly retrieve and format arbitrary records. It
must never be tied to a console because it has nothing to do with
consoles (as can bee seen with the devkmsg_read() hack you added in the
function).

I recommend adding an extra argument specifying the level.

The extra argument would be redundant if may_suppress=false. So perhaps
as an alternative change "bool may_suppress" to "u32 supress_level". The
loglevels are only 3 bits. So you could easily define a special value
NO_SUPPRESS to represent the may_suppress=false case.

#define NO_SUPPRESS BIT(31)

bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
                             bool is_extended, u32 suppress_level);

Then in devkmsg_read():

printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, NO_SUPRRESS)

John Ogness