Return-Path: Message-ID: <54D03996.1070503@sunrus.com.cn> Date: Tue, 03 Feb 2015 10:59:34 +0800 From: Chen Gang S MIME-Version: 1.0 To: Joe Perches CC: marcel@holtmann.org, gustavo@padovan.org, johan.hedberg@gmail.com, "David S. Miller" , linux-bluetooth@vger.kernel.org, "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] net: bluetooth: hci_sock: Use 'const void *' instead of 'void *' for 2nd parameter of hci_test_bit() References: <54CFE8BE.5030700@sunrus.com.cn> <1422912017.30476.28.camel@perches.com> <54D0332B.6050701@sunrus.com.cn> In-Reply-To: <54D0332B.6050701@sunrus.com.cn> Content-Type: text/plain; charset=windows-1252 List-ID: On 2/3/15 10:32, Chen Gang S wrote: > On 2/3/15 05:20, Joe Perches wrote: >> On Tue, 2015-02-03 at 05:14 +0800, Chen Gang S wrote: >>> hci_test_bit() does not modify 2nd parameter, so it is better to let it >>> be constant, or may cause build warning. The related warning (with >>> allmodconfig under xtensa): >> [] >>> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c >> [] >>> @@ -46,7 +46,7 @@ struct hci_pinfo { >>> unsigned short channel; >>> }; >>> >>> -static inline int hci_test_bit(int nr, void *addr) >>> +static inline int hci_test_bit(int nr, const void *addr) >>> { >>> return *((__u32 *) addr + (nr >> 5)) & ((__u32) 1 << (nr & 31)); >>> } >> >> It's probably better to use const __u32 * here too, but the >> real thing I wonder is whether or not there's an issue with >> one of the 2 uses of this function. >> >> One of them passes a unsigned long *, the other a u32 *. >> >> $ git grep -w hci_test_bit >> net/bluetooth/hci_sock.c:static inline int hci_test_bit(int nr, void *addr) >> net/bluetooth/hci_sock.c: if (!hci_test_bit(flt_event, &flt->event_mask)) >> net/bluetooth/hci_sock.c: !hci_test_bit(ocf & HCI_FLT_OCF_BITS, >> net/bluetooth/hci_sock.c- &hci_sec_filter.ocf_mask[ogf])) && >> >> hci_sec_filter.ocf_mask is __u32 >> but flt->event_mask is unsigned long. >> >> Any possible issue here on 64-bit systems? >> > > For me, it can not cause issue on 64-bit systems. hci_test_bit() treats > 'addr' as "__u32 *", and has to use the pointer to do something. > 'event_mask' is intended to type cast to "__u32 *" within 'hci_sock.c'. So for me, "const __u32 *" is better than "const void *" for 2nd parameter of hci_test_bit(). If what I said above is correct, and also if necessary, I shall patch v3 for it. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed