Messages in this thread | | | Date | Sun, 18 Jan 2015 15:12:21 -0500 | From | "Ahmed S. Darwish" <> | Subject | Re: [PATCH v4 3/4] can: kvaser_usb: Add support for the Usbcan-II family |
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Hi!
On Mon, Jan 12, 2015 at 02:53:02PM +0100, Olivier Sobrie wrote: > Hello, > > On Sun, Jan 11, 2015 at 03:36:12PM -0500, Ahmed S. Darwish wrote: > > From: Ahmed S. Darwish <ahmed.darwish@valeo.com> > >
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> > @@ -98,7 +128,13 @@ > > #define CMD_START_CHIP_REPLY 27 > > #define CMD_STOP_CHIP 28 > > #define CMD_STOP_CHIP_REPLY 29 > > -#define CMD_GET_CARD_INFO2 32 > > +#define CMD_READ_CLOCK 30 > > +#define CMD_READ_CLOCK_REPLY 31 > > These two defines are not used. >
They were added for completeness: the only gap in our continuous sequence of command IDs from 12 to 39 ;-) No big deal, to be removed in the next submission.
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> > + > > +struct kvaser_msg_tx_acknowledge_header { > > + u8 channel; > > + u8 tid; > > +}; > > Is this struct really needed? Can't you simply use > leaf_msg_tx_acknowledge or usbcan_msg_tx_acknowledge > structures to read the header. > Same for kvaser_msg_rx_can_header. >
They're added to ensure type-safety throughout the code. Basically they're the common part of a command that has different wire format between the Leaf and the USBCan, but share a common header. Such notation was only added when it was strictly necessary.
For example, there are three functions where 'rx_can_header' is referenced in the driver, and one function where 'tx_acknowledge_header' is referenced. Without such header structure, I'll have to sprinkle 3 to 4 extra blocks of:
switch (dev->family) { case KVASER_LEAF: case KVASER_USBCAN: }
which would be _really_ ugly. The *_header notation ensures that, in the body of each function, we're accessing the fields in a very safe manner.
Thanks, Darwish
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