linux-kernel - staging: r8188eu: struct rt_firmware

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Date:   Wed, 13 Apr 2022 18:27:28 +0200
From:   Michael Straube <straube.linux@...il.com>
To:     Larry Finger <Larry.Finger@...inger.net>
Cc:     Phillip Potter <phil@...lpotter.co.uk>,
        Greg KH <gregkh@...uxfoundation.org>,
        "open list:STAGING SUBSYSTEM" <linux-staging@...ts.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        straube.linux@...il.com
Subject: staging: r8188eu: struct rt_firmware_header issues

Hi all,

I think the rt_firmware_hdr structure in rtw_fw.c has some issues.


struct rt_firmware_hdr {
	/*  8-byte alinment required */
	/*  LONG WORD 0 ---- */
	__le16		Signature;	/* 92C0: test chip; 92C,
					 * 88C0: test chip; 88C1: MP A-cut;
					 * 92C1: MP A-cut */
	u8		Category;	/*  AP/NIC and USB/PCI */
	u8		Function;	/*  Reserved for different FW function
					 *  indcation, for further use when
					 *  driver needs to download different
					 *  FW for different conditions */
	__le16		Version;	/*  FW Version */
	u8		Subversion;	/*  FW Subversion, default 0x00 */
	u16		Rsvd1;

	/*  LONG WORD 1 ---- */
	u8		Month;	/*  Release time Month field */
	u8		Date;	/*  Release time Date field */
	u8		Hour;	/*  Release time Hour field */
	u8		Minute;	/*  Release time Minute field */
	__le16		RamCodeSize;	/*  The size of RAM code */
	u8		Foundry;
	u8		Rsvd2;

	/*  LONG WORD 2 ---- */
	__le32		SvnIdx;	/*  The SVN entry index */
	u32		Rsvd3;

	/*  LONG WORD 3 ---- */
	u32		Rsvd4;
	u32		Rsvd5;
};


Then we have in rtl8188e_firmware_download():


	fwhdr = (struct rt_firmware_hdr *)dvobj->firmware.data;

	<snip>

	if (IS_FW_HEADER_EXIST(fwhdr)) {
		/*  Shift 32 bytes for FW header */
		fw_data = fw_data + 32;
		fw_size = fw_size - 32;
	}

We add/sub 32 bytes but the size of struct rt_firmware_hdr is actually
33 bytes. I noticed this when I wanted to replace:

		fw_data = fw_data + 32;
		fw_size = fw_size - 32;

with:
		fw_data = fw_data + sizeof(struct rt_firmware_hdr);
		fw_size = fw_size - sizeof(struct rt_firmware_hdr);;

To me it looks add/sub 32 is correct here but the struct is
wrong. I don't know if the firmware for this driver is so much different
from firmware for the drivers in drivers/net/wireless/realtek/rtlwifi.
They use a struct of size 32.

Also, souldn't the u16 and u32 variables in the struct be __le16 and
__le32 ?

I wonder if we can just use the rtlwifi_firmware_header structure from
drivers/net/wireless/realtek/rtlwifi/wifi.h ?

Comments from people with better knowledge appreciated. :)

regards,
Michael