netdev - Re: [PATCH 03/34] brcmfmac: firmware: Support having multiple alt paths

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Date:   Sun, 2 Jan 2022 23:12:41 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Hector Martin <marcan@...can.st>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>
Cc:     Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Rafał Miłecki <zajec5@...il.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        "brian m. carlson" <sandals@...stytoothpaste.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com
Subject: Re: [PATCH 03/34] brcmfmac: firmware: Support having multiple alt
 paths

02.01.2022 17:25, Hector Martin пишет:
> On 2022/01/02 16:08, Dmitry Osipenko wrote:
>> 26.12.2021 18:35, Hector Martin пишет:
>>> +static void brcm_free_alt_fw_paths(const char **alt_paths)
>>> +{
>>> +	int i;
>>> +
>>> +	if (!alt_paths)
>>> +		return;
>>> +
>>> +	for (i = 0; alt_paths[i]; i++)
>>> +		kfree(alt_paths[i]);
>>> +
>>> +	kfree(alt_paths);
>>>  }
>>>  
>>>  static int brcmf_fw_request_firmware(const struct firmware **fw,
>>>  				     struct brcmf_fw *fwctx)
>>>  {
>>>  	struct brcmf_fw_item *cur = &fwctx->req->items[fwctx->curpos];
>>> -	int ret;
>>> +	int ret, i;
>>>  
>>>  	/* Files can be board-specific, first try a board-specific path */
>>>  	if (cur->type == BRCMF_FW_TYPE_NVRAM && fwctx->req->board_type) {
>>> -		char *alt_path;
>>> +		const char **alt_paths = brcm_alt_fw_paths(cur->path, fwctx);
>>>  
>>> -		alt_path = brcm_alt_fw_path(cur->path, fwctx->req->board_type);
>>> -		if (!alt_path)
>>> +		if (!alt_paths)
>>>  			goto fallback;
>>>  
>>> -		ret = request_firmware(fw, alt_path, fwctx->dev);
>>> -		kfree(alt_path);
>>> -		if (ret == 0)
>>> -			return ret;
>>> +		for (i = 0; alt_paths[i]; i++) {
>>> +			ret = firmware_request_nowarn(fw, alt_paths[i], fwctx->dev);
>>> +			if (ret == 0) {
>>> +				brcm_free_alt_fw_paths(alt_paths);
>>> +				return ret;
>>> +			}
>>> +		}
>>> +		brcm_free_alt_fw_paths(alt_paths);
>>>  	}
>>>  
>>>  fallback:
>>> @@ -641,6 +663,9 @@ static void brcmf_fw_request_done(const struct firmware *fw, void *ctx)
>>>  	struct brcmf_fw *fwctx = ctx;
>>>  	int ret;
>>>  
>>> +	brcm_free_alt_fw_paths(fwctx->alt_paths);
>>> +	fwctx->alt_paths = NULL;
>>
>> It looks suspicious that fwctx->alt_paths isn't zero'ed by other code
>> paths. The brcm_free_alt_fw_paths() should take fwctx for the argument
>> and fwctx->alt_paths should be set to NULL there.
> 
> There are multiple code paths for alt_paths; the initial firmware lookup
> uses fwctx->alt_paths, and once we know the firmware load succeeded we
> use blocking firmware requests for NVRAM/CLM/etc and those do not use
> the fwctx member, but rather just keep alt_paths in function scope
> (brcmf_fw_request_firmware). You're right that there was a rebase SNAFU
> there though, I'll compile test each patch before sending v2. Sorry
> about that. In this series the code should build again by patch #6.
> 
> Are you thinking of any particular code paths? As far as I saw when
> writing this, brcmf_fw_request_done() should always get called whether
> things succeed or fail. There are no other code paths that free
> fwctx->alt_paths.

It should be okay in the particular case then. But this is not obvious
without taking a closer look at the code, which is a sign that there is
some room for improvement.

>> On the other hand, I'd change the **alt_paths to a fixed-size array.
>> This should simplify the code, making it easier to follow and maintain.
>>
>> -	const char **alt_paths;
>> +	char *alt_paths[BRCM_MAX_ALT_FW_PATHS];
>>
>> Then you also won't need to NULL-terminate the array, which is a common
>> source of bugs in kernel.
> 
> That sounds reasonable, it'll certainly make the code simpler. I'll do
> that for v2.

Feel free to CC me on v2. I'll take a closer look and give a test to the
patches on older hardware, checking for regressions.