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

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Date:   Tue, 26 Oct 2021 14:11:51 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>, amit@...nel.org, arnd@...db.de,
        osandov@...com, 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()


在 2021/10/26 下午2:10, Greg KH 写道:
> On Tue, Oct 26, 2021 at 02:02:21PM +0800, Xianting Tian wrote:
>> 在 2021/10/26 下午1:10, Jiri Slaby 写道:
>>> 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.
>> I mentioned such info in the commit log:
>> 'Introduce another array(cons_hvcs[]) for hvc pointers next to the
>> cons_ops[] and vtermnos[] arrays. With the array, we can easily find
>> hvc's cons_outbuf and its lock.'
>>
>> After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method.
>> I send a patch to fix the issue?  or these serial pathches reverted fisrtly then I resend new version patches? thanks
> Let me revert these now and you can send an updated version.
OK, thanks.
>
> thanks,
>
> greg k-h