linux-kernel - Re: [PATCH v11 2/3] tty: hvc: pass DMA capable memory to put

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Date:   Tue, 26 Oct 2021 07:10:54 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Xianting Tian <xianting.tian@...ux.alibaba.com>,
        gregkh@...uxfoundation.org, amit@...nel.org, arnd@...db.de,
        osandov@...com
Cc:     shile.zhang@...ux.alibaba.com, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 2/3] tty: hvc: pass DMA capable memory to put_chars()

On 15. 10. 21, 4:46, Xianting Tian wrote:
> @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
>   static void hvc_console_print(struct console *co, const char *b,
>   			      unsigned count)
>   {
> -	char c[N_OUTBUF] __ALIGNED__;
> +	char *c;
>   	unsigned i = 0, n = 0;
>   	int r, donecr = 0, index = co->index;
> +	unsigned long flags;
> +	struct hvc_struct *hp;
>   
>   	/* Console access attempt outside of acceptable console range. */
>   	if (index >= MAX_NR_HVC_CONSOLES)
> @@ -163,6 +156,13 @@ static void hvc_console_print(struct console *co, const char *b,
>   	if (vtermnos[index] == -1)
>   		return;
>   
> +	hp = cons_hvcs[index];
> +	if (!hp)
> +		return;

You effectively make the console unusable until someone calls 
hvc_alloc() for this device, correct? This doesn't look right. Neither 
you describe this change of behaviour in the commit log.

regards,
-- 
js
suse labs