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

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Message-ID: <f1b92c7d-0eaf-4eac-ecd2-fbb74fb63b52@kernel.org>
Date:   Thu, 5 Aug 2021 10:09:47 +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:     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()

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