Re: [PATCH v3 2/5] staging: r8188eu: cast to restricted __be32

[Larry Finger]

On 8/23/21 3:44 AM, Aakash Hemadri wrote:
> On 21/08/21 09:48PM, Aakash Hemadri wrote:
> > Fix sparse warning:
> > > rtw_br_ext.c:836:54: warning: cast to restricted __be32
> >
> > dhpch->cookie is be32, change it's type.
> >
> > Suggested-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
> > Signed-off-by: Aakash Hemadri <aakashhemadri123@xxxxxxxxx>
> > ---
> >   drivers/staging/r8188eu/core/rtw_br_ext.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
> > index f6d1f6029ec3..f65d94bfa286 100644
> > --- a/drivers/staging/r8188eu/core/rtw_br_ext.c
> > +++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
> > @@ -649,7 +649,7 @@ struct dhcpMessage {
> >   	u_int8_t chaddr[16];
> >   	u_int8_t sname[64];
> >   	u_int8_t file[128];
> > -	u_int32_t cookie;
> > +	__be32 cookie;
> >   	u_int8_t options[308]; /* 312 - cookie */
> >   };
> >   
> > @@ -671,7 +671,7 @@ void dhcp_flag_bcast(struct adapter *priv, struct sk_buff *skb)
> >   				    (udph->dest == __constant_htons(SERVER_PORT))) { /*  DHCP request */
> >   					struct dhcpMessage *dhcph =
> >   						(struct dhcpMessage *)((size_t)udph + sizeof(struct udphdr));
> > -					u32 cookie = be32_to_cpu((__be32)dhcph->cookie);
> > +					u32 cookie = be32_to_cpu(dhcph->cookie);
> >   
> >   					if (cookie == DHCP_MAGIC) { /*  match magic word */
> >   						if (!(dhcph->flags & htons(BROADCAST_FLAG))) {
> > --
> > 2.32.0
>
> David Laight suggested to use get_unaligned_be32, I am not sure if it's
> the right thing to do because as far as I understand get_unaligned_be32
> byteshifts the argument.
>
> Can someone please confirm if this change is okay?

It is not needed. variable dhcph->cookie is 4-byte aligned. Usind the unaligned 
version would just add cpu cycles and arrivw at the same point!

Larry