linux-kernel - Re: [PATCH] hns3: work around stack size warning

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Message-Id: <4019926a-6d2a-48e8-aad3-bc0d0b6e28eb@app.fastmail.com>
Date: Mon, 23 Jun 2025 09:12:35 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Jijie Shao" <shaojijie@...wei.com>, "Jakub Kicinski" <kuba@...nel.org>
Cc: "Jian Shen" <shenjian15@...wei.com>,
 "Salil Mehta" <salil.mehta@...wei.com>,
 "Andrew Lunn" <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>,
 "Eric Dumazet" <edumazet@...gle.com>, "Paolo Abeni" <pabeni@...hat.com>,
 "Nathan Chancellor" <nathan@...nel.org>,
 "Nick Desaulniers" <nick.desaulniers+lkml@...il.com>,
 "Bill Wendling" <morbo@...gle.com>, "Justin Stitt" <justinstitt@...gle.com>,
 "Hao Lan" <lanhao@...wei.com>, "Guangwei Zhang" <zhangwangwei6@...wei.com>,
 Netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH] hns3: work around stack size warning

On Mon, Jun 23, 2025, at 08:21, Jijie Shao wrote:
> on 2025/6/23 13:56, Arnd Bergmann wrote:
>>
>>> -    sprintf(result[j++], "%u", index);
>>> -    sprintf(result[j++], "%u", readl_relaxed(ring->tqp->io_base +
>>> -        HNS3_RING_TX_RING_BD_NUM_REG));
>>> +    seq_printf(s, "%-4u%6s", index, " ");
>>> +    seq_printf(s, "%-5u%3s",
>>> +           readl_relaxed(base + HNS3_RING_TX_RING_BD_NUM_REG), " ");
>> I'm not sure I understand the format string changes here, I did
>> not think they were necessary.
>>
>> Are you doing this to keep the output the same as before, or are
>> you reformatting the contents for readability?
>
> yeah, just to keep the output the same as before

Ok. 

>>> +static int hns3_dbg_common_init_t1(struct hnae3_handle *handle, u32
>>> cmd)
>>> +{
>>> +    struct device *dev = &handle->pdev->dev;
>>> +    struct dentry *entry_dir;
>>> +    read_func func = NULL;
>>> +
>>> +    switch (hns3_dbg_cmd[cmd].cmd) {
>>> +    case HNAE3_DBG_CMD_TX_QUEUE_INFO:
>>> +        func = hns3_dbg_tx_queue_info;
>>> +        break;
>>> +    default:
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    entry_dir = hns3_dbg_dentry[hns3_dbg_cmd[cmd].dentry].dentry;
>>> +    debugfs_create_devm_seqfile(dev, hns3_dbg_cmd[cmd].name, entry_dir,
>>> +                    func);
>>> +
>>> +    return 0;
>> This will work fine as well, but I think you can do slightly better
>> by having your own file_operations with a read function based
>> on single_open() and your current hns3_dbg_read_cmd().
>>
>> I don't think you gain anything from using debugfs_create_devm_seqfile()
>> since you use debugfs_remove_recursive() for cleaning it up anyway.
>
> Using debugfs_create_devm_seqfile() is just to simplify the code.
> We only need to focus on the implementation of .read() function.

What I meant is that it doesn't seem simpler to me, as it adds one
level of indirection to both the file creation and the read()
function compared to having a single_open() helpe with that
switch()/case or the corresponding hns3_dbg_cmd_func[] array.

Either way, I'm not worried about it, there is no actual problem
that I see with your version.

     Arnd