Re: [Xen-devel] [PATCH v2] ns16550: misc minor adjustments

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 12/11/15 15:34, Jan Beulich wrote:
> First and foremost: fix documentation: The use of "clock_hz", when
> "base_baud" was meant, has taken me several hours (suspecting a more
> complicated problem with the PCIe card I've been trying to get
> working). At once correct the "gdb" option, which is more like
> "console", not like "com<N>".
>
> Next, fix the types of ns_{read,write}_reg(): Especially the former
> having had a signed return type so far caused quite interesting effects
> when determining to baud rate if "auto" was specified. In that same
> code, also avoid dividing by zero when in fact the baud rate was not
> previously set up.
>
> Further, accept I/O port based serial PCI cards with a port range wider
> than 8 bytes.
>
> Finally, slightly rearrange struct ns16550 to reduce holes.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> with one tweak

> ---
> v2: Log a message when reading zero divisor. Make an attempt at
>     explaining what "base baud rate" means.
>
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -277,13 +277,14 @@ Flag to indicate whether to probe for a
>  ACPI indicating none to be there.
>  
>  ### com1,com2
> -> `= 
> <baud>[/<clock_hz>][,[DPS][,[<io-base>|pci|amt][,[<irq>][,[<port-bdf>][,[<bridge-bdf>]]]]]]`
> +> `= 
> <baud>[/<base-baud>][,[DPS][,[<io-base>|pci|amt][,[<irq>][,[<port-bdf>][,[<bridge-bdf>]]]]]]`
>  
>  Both option `com1` and `com2` follow the same format.
>  
>  * `<baud>` may be either an integer baud rate, or the string `auto` if
>    the bootloader or other earlier firmware has already set it up.
> -* Optionally, a clock speed measured in hz can be specified.
> +* Optionally, the base baud rate (usually the highest baud rate the
> +  device can communicate at) can be specified.
>  * `DPS` represents the number of data bits, the parity, and the number
>    of stop bits.
>    * `D` is an integer between 5 and 8 for the number of data bits.
> @@ -730,9 +731,11 @@ Controls EPT related features.
>  >> Have hardware keep accessed/dirty (A/D) bits updated.
>  
>  ### gdb
> -> `= 
> <baud>[/<clock_hz>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]] | 
> pci | amt ] `
> +> `= com1[H,L] | com2[H,L] | dbgp`
>  
> -Specify the serial parameters for the GDB stub.
> +> Default: ``
> +
> +Specify which console gdbstub should use. See `console`.

Elsewhere in the document, bold is used to refer to other options, so
"see **console**".

~Andrew

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