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

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Message-ID: <f35bed9b-aefd-cdf1-500f-194d5699cffd@marcan.st>
Date:   Sun, 2 Jan 2022 23:25:27 +0900
From:   Hector Martin <marcan@...can.st>
To:     Dmitry Osipenko <digetx@...il.com>,
        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

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.

> 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.


-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub