On Fri, May 18, 2018 at 02:48:11PM +0000, guido@xxxxxxxxxxxxxxxxxx wrote:
>
> Zitat von Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>:
>
> > On Thu, May 17, 2018 at 07:03:30PM +0200, Guido Kiener wrote:
> > > +/*
> > > + * usbtmc_message->flags:
> > > + */
> > > +#define USBTMC_FLAG_ASYNC 0x0001
> > > +#define USBTMC_FLAG_APPEND 0x0002
> > > +#define USBTMC_FLAG_IGNORE_TRAILER 0x0004
> > > +
> > > +struct usbtmc_message {
> > > + void __user *message; /* pointer to header and data */
> > > + __u64 transfer_size; /* size of bytes to transfer */
> > > + __u64 transferred; /* size of received/written bytes */
> > > + __u32 flags; /* bit 0: 0 = synchronous; 1 = asynchronous */
> > > +} __attribute__ ((packed));
> >
> > Very odd structure. Your userspace pointer is going to be totally out
> > of alignment on 32bit systems running on a 64bit kernel. Why have a
> > separate pointer at all? Why not just put the mesage at the end of this
> > structure directly with something like:
> > __u8 message[0];
> > ?
> >
>
> Oh yes, I should know that from another project. Indead we did not test it
> with 32 bit applications on 64 platforms.
>
> When we use your proposal then we just can use
> #define USBTMC_IOCTL_WRITE _IO(USBTMC_IOC_NR, 13)?
Why 13? Use the structure please, that way you know you always get it
right.
thanks,
greg k-h
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