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Subject: Re: [PATCH v3 1/2] tty: hvc: pass DMA capable memory to put_chars()
From:   Jiri Slaby <jirislaby@kernel.org>
To:     Xianting Tian <xianting.tian@linux.alibaba.com>,
        gregkh@linuxfoundation.org, amit@kernel.org, arnd@arndb.de,
        osandov@fb.com
Cc:     linuxppc-dev@lists.ozlabs.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20210804025453.93543-1-xianting.tian@linux.alibaba.com>
 <0f26a1c3-53e8-9282-69e8-8d81a9cafc59@kernel.org>
Message-ID: <f1b92c7d-0eaf-4eac-ecd2-fbb74fb63b52@kernel.org>
Date:   Thu, 5 Aug 2021 10:09:47 +0200
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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.

>> +??? /*
>> +???? * 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?

> 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,
-- 
js
suse labs