From: Alan Stern <stern@rowland.harvard.edu>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH 08/15] usb: ehci: avoid gcc-10 zero-length-bounds warning
Date: Fri, 1 May 2020 16:10:03 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.2005011609140.903-100000@netrider.rowland.org> (raw)
In-Reply-To: <CAK8P3a19DSnyvzSRCFr6fQGAMudQwhZY7Wy2yS6HL8y3TsfoLw@mail.gmail.com>
On Fri, 1 May 2020, Arnd Bergmann wrote:
> On Fri, May 1, 2020 at 4:42 AM Alan Stern <stern@rowland.harvard.edu> wrote:
> > On Thu, 30 Apr 2020, Arnd Bergmann wrote:
>
> >
> > No, they don't.
>
> > > /* PORTSC: offset 0x44 */
> > > - u32 port_status[0]; /* up to N_PORTS */
> > > + union {
> > > + u32 port_status[9]; /* up to N_PORTS */
> >
> > This array can have up to 15 elements, meaning that it can extend out
> > to offset 0x80.
>
> Ok, thanks for the clarification!
>
> > > /* EHCI 1.1 addendum */
> > > #define PORTSC_SUSPEND_STS_ACK 0
> > > #define PORTSC_SUSPEND_STS_NYET 1
> > > @@ -165,7 +166,8 @@ struct ehci_regs {
> > > #define PORT_CONNECT (1<<0) /* device connected */
> > > #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC)
> > >
> > > - u32 reserved3[9];
> > > + u32 reserved3[9];
> > > + };
> > >
> > > /* USBMODE: offset 0x68 */
> > > u32 usbmode; /* USB Device mode */
> >
> > As you see, this next field actually lies inside the preceding array.
> > It's not a real conflict; any hardware which supports the usbmode field
> > uses only the first element of the port_status array.
> >
> > I don't know how you want to handle this. Doing
> >
> > #define usbmode port_status[9]
> >
> > doesn't seem like a very good approach, but I can't think of anything
> > better at the moment. Maybe just set the array size to 9, as you did,
> > but with a comment explaining what's really going on.
>
> The easiest change would be to use an anonymous struct like this
>
> /* PORTSC: offset 0x44 */
> union {
> u32 port_status[15]; /* up to N_PORTS */
> /* EHCI 1.1 addendum */
> #define PORTSC_SUSPEND_STS_ACK 0
> ...
> #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC)
> struct {
> u32 reserved3[9];
>
> /* USBMODE: offset 0x68 */
> u32 usbmode; /* USB Device mode */
> #define USBMODE_SDIS (1<<3) /* Stream disable */
> #define USBMODE_BE (1<<2) /* BE/LE endianness select */
> #define USBMODE_CM_HC (3<<0) /* host controller mode */
> #define USBMODE_CM_IDLE (0<<0) /* idle state */
>
> u32 reserved4[5];
> };
> };
> u32 reserved5;
>
> It doesn't really improve readability, but it should correctly
> reflect the layout as you described it.
Sounds good. Please go ahead and update the patch.
Alan Stern
next prev parent reply other threads:[~2020-05-01 20:10 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 21:30 [PATCH 00/15] gcc-10 warning fixes Arnd Bergmann
2020-04-30 21:30 ` [PATCH 01/15] crypto - Avoid free() namespace collision Arnd Bergmann
2020-05-08 6:06 ` Herbert Xu
2020-04-30 21:30 ` [PATCH 02/15] iwlwifi: mvm: fix gcc-10 zero-length-bounds warning Arnd Bergmann
2020-06-10 12:18 ` Luciano Coelho
2020-04-30 21:30 ` [PATCH 03/15] mwifiex: avoid -Wstringop-overflow warning Arnd Bergmann
2020-05-06 8:43 ` Kalle Valo
2020-04-30 21:30 ` [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings Arnd Bergmann
2020-04-30 21:45 ` Gustavo A. R. Silva
2020-04-30 21:44 ` Arnd Bergmann
2020-05-04 11:54 ` Kalle Valo
2020-05-04 16:09 ` Gustavo A. R. Silva
2020-05-05 4:56 ` Kalle Valo
2020-04-30 21:30 ` [PATCH 05/15] bpf: avoid gcc-10 stringop-overflow warning Arnd Bergmann
2020-05-04 21:06 ` Daniel Borkmann
2020-04-30 21:30 ` [PATCH 06/15] netfilter: conntrack: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-05-10 21:48 ` Pablo Neira Ayuso
2020-04-30 21:30 ` [PATCH 07/15] drop_monitor: work around gcc-10 stringop-overflow warning Arnd Bergmann
2020-05-01 11:28 ` Neil Horman
2020-04-30 21:30 ` [PATCH 08/15] usb: ehci: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-05-01 2:42 ` Alan Stern
2020-05-01 20:06 ` Arnd Bergmann
2020-05-01 20:10 ` Alan Stern [this message]
2020-04-30 21:30 ` [PATCH 09/15] udf: avoid gcc-10 zero-length-bounds warnings Arnd Bergmann
2020-04-30 21:54 ` Pali Rohár
2020-05-01 20:30 ` Arnd Bergmann
2020-05-01 20:48 ` Jan Kara
2020-05-01 20:57 ` Pali Rohár
2020-04-30 21:30 ` [PATCH 10/15] hpfs: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-04-30 21:30 ` [PATCH 11/15] omfs: avoid gcc-10 stringop-overflow warning Arnd Bergmann
2020-04-30 21:30 ` [PATCH 12/15] media: s5k5baf: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-04-30 21:46 ` Gustavo A. R. Silva
2020-04-30 21:30 ` [PATCH 13/15] scsi: sas: " Arnd Bergmann
2020-05-01 7:47 ` John Garry
2020-05-01 7:54 ` Arnd Bergmann
2020-05-01 14:53 ` James Bottomley
2020-05-01 17:36 ` Arnd Bergmann
2020-04-30 21:30 ` [PATCH 14/15] isci: " Arnd Bergmann
2020-04-30 21:30 ` [PATCH 15/15] nvme: " Arnd Bergmann
2020-05-01 7:32 ` Christoph Hellwig
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