RE: [PATCH v3 5/8] thunderbolt: Communication with the ICM (firmware)

[Winkler, Tomas]

> -----Original Message-----
> From: Levy, Amir (Jer)
> Sent: Thursday, July 14, 2016 17:50
> To: Winkler, Tomas <tomas.winkler@xxxxxxxxx>;
> andreas.noever@xxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
> bhelgaas@xxxxxxxxxx
> Cc: linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; thunderbolt-linux <thunderbolt-linux@xxxxxxxxx>;
> Westerberg, Mika <mika.westerberg@xxxxxxxxx>
> Subject: RE: [PATCH v3 5/8] thunderbolt: Communication with the ICM
> (firmware)
> 
> Hi Tomas,
> Thanks for your comments.
> 
> On Thu, Jul 14 2016, 03:44 PM, Winkler, Tomas wrote:
> > > +/* NHI genetlink commands */
> > > +enum {
> > > +	NHI_CMD_UNSPEC,
> > > +	NHI_CMD_SUBSCRIBE,
> > > +	NHI_CMD_UNSUBSCRIBE,
> > > +	NHI_CMD_QUERY_INFORMATION,
> > > +	NHI_CMD_MSG_TO_ICM,
> > > +	NHI_CMD_MSG_FROM_ICM,
> > > +	NHI_CMD_MAILBOX,
> > > +	NHI_CMD_APPROVE_TBT_NETWORKING,
> > > +	NHI_CMD_ICM_IN_SAFE_MODE,
> > > +	__NHI_CMD_MAX,
> > > +};
> > > +#define NHI_CMD_MAX (__NHI_CMD_MAX - 1)
> > NHI_CMD_MAX  = NHI_CMD_ICM_IN_SAFE_MODE ?
> >
> 
> This template is used a lot with (generic) netlink.
> Few examples:
> http://lxr.free-electrons.com/source/drivers/acpi/event.c#L62
> http://lxr.free-electrons.com/source/include/uapi/linux/irda.h#L224
> It is easier to maintain - adding entry in the list will automatically update
> MAX.

Fair enough. 

> [...]
> 
> > > +		u32 status;
> > > +
> > > +		status = ioread32(nhi_ctxt->iobase + REG_FW_STS);
> > > +
> > > +		if (status & REG_FW_STS_NVM_AUTH_DONE)
> > > +			break;
> > > +		msleep(30);
> >
> > 30 is  big number, for polling, what is behind this?
> >
> 
> The NVM authentication can take time for ICM.
> This number comes from experiments.

This deserve some comment, this look very random. 
 
> [...]
> 
> > > +static struct tbt_nhi_ctxt *nhi_search_ctxt(u32 id) {
> > > +	struct tbt_nhi_ctxt *nhi_ctxt;
> > > +
> > > +	list_for_each_entry(nhi_ctxt, &controllers_list, node)
> > > +		if (nhi_ctxt->id == id)
> > > +			return nhi_ctxt;
> >
> > Don't you need to lock this list with the controllers_list_rwsem ?
> >
> 
> This is a helper function for searching the list.
> The callers take and release the lock.

Since this doesn't fit the patterns in your code, the function deserves a comment, that it should be used under lock. 

> 
> [...]
> 
> > > +	bool nvm_auth_on_boot : 1;
> > Don't use bool with bit fields use u32
> 
> What is the concern here?
> If it is size of bool, it doesn't matter for this struct.
> It is more readable that the expected value is bool, and it is used a lot in
> kernel, for example:
> http://lxr.free-electrons.com/source/include/linux/pm.h#L558

Hmm, actually a nice feature I wasn't aware of, save some space and got bool type checking. 

Thanks