linux-kernel - Re: [PATCH v3 1/2] tty: hvc: pass DMA capable memory to put

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Message-ID: <202cf491-5cdd-999f-d556-a5ebd2b4e266@linux.alibaba.com>
Date:   Thu, 5 Aug 2021 19:14:13 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     Jiri Slaby <jirislaby@...nel.org>, gregkh@...uxfoundation.org,
        amit@...nel.org, arnd@...db.de, osandov@...com
Cc:     linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] tty: hvc: pass DMA capable memory to put_chars()


在 2021/8/5 下午4:09, Jiri Slaby 写道:
> On 05. 08. 21, 9:58, Jiri Slaby wrote:
>> Hi,
>>
>> On 04. 08. 21, 4:54, Xianting Tian wrote:
>>> @@ -933,6 +949,16 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, 
>>> int data,
>>>       hp->outbuf_size = outbuf_size;
>>>       hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
>
> This deserves cleanup too. Why is "outbuf" not "char outbuf[0] 
> __ALIGNED__" at the end of the structure? The allocation would be 
> easier (using struct_size()) and this line would be gone completely.
I will make the cleanup in v4.
>
>>> +    /*
>>> +     * hvc_con_outbuf is guaranteed to be aligned at least to the
>>> +     * size(N_OUTBUF) by kmalloc().
>>> +     */
>>> +    hp->hvc_con_outbuf = kzalloc(N_OUTBUF, GFP_KERNEL);
>>> +    if (!hp->hvc_con_outbuf)
>>> +        return ERR_PTR(-ENOMEM);
>>
>> This leaks hp, right?
>
> Actually, why don't you make
> char c[N_OUTBUF] __ALIGNED__;
>
> part of struct hvc_struct directly?
thanks, it a good idea, I will change it in v4.
>
>> BTW your 2 patches are still not threaded, that is hard to follow.
>>
>>> +
>>> +    spin_lock_init(&hp->hvc_con_lock);
>>> +
>>>       tty_port_init(&hp->port);
>>>       hp->port.ops = &hvc_port_ops;
>>
>> thanks,