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SubjectRE: [PATCH v3 2/5] i3c: master: make sure ->boardinfo is initialized in add_i3c_dev_locked()
Date
Hi Boris,

From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Thu, Oct 03, 2019 at 15:29:43

> On Thu, 5 Sep 2019 12:00:35 +0200
> Vitor Soares <Vitor.Soares@synopsys.com> wrote:
>
> > The newdev->boardinfo assignment was missing in
> > i3c_master_add_i3c_dev_locked() and hence the ->of_node info isn't
> > propagated to i3c_dev_desc.
> >
> > Fix this by trying to initialize device i3c_dev_boardinfo if available.
> >
> > Cc: <stable@vger.kernel.org>
> > Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure")
> > Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
> > ---
> > Change in v3:
> > - None
> >
> > Changes in v2:
> > - Change commit message
> > - Change i3c_master_search_i3c_boardinfo(newdev) to
> > i3c_master_init_i3c_dev_boardinfo(newdev)
> > - Add fixes, stable tags
> >
> > /**
> > * i3c_master_add_i3c_dev_locked() - add an I3C slave to the bus
> > * @master: master used to send frames on the bus
> > @@ -1818,8 +1834,9 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > u8 addr)
> > {
> > struct i3c_device_info info = { .dyn_addr = addr };
> > - struct i3c_dev_desc *newdev, *olddev;
> > u8 old_dyn_addr = addr, expected_dyn_addr;
> > + enum i3c_addr_slot_status addrstatus;
> > + struct i3c_dev_desc *newdev, *olddev;
> > struct i3c_ibi_setup ibireq = { };
> > bool enable_ibi = false;
> > int ret;
> > @@ -1878,6 +1895,8 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > if (ret)
> > goto err_detach_dev;
> >
> > + i3c_master_init_i3c_dev_boardinfo(newdev);
> > +
> > /*
> > * Depending on our previous state, the expected dynamic address might
> > * differ:
> > @@ -1895,7 +1914,11 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > else
> > expected_dyn_addr = newdev->info.dyn_addr;
> >
> > - if (newdev->info.dyn_addr != expected_dyn_addr) {
> > + addrstatus = i3c_bus_get_addr_slot_status(&master->bus,
> > + expected_dyn_addr);
> > +
> > + if (newdev->info.dyn_addr != expected_dyn_addr &&
> > + addrstatus == I3C_ADDR_SLOT_FREE) {
>
> First, this change shouldn't be part of this patch, since the commit
> message only mentions the boardinfo init stuff,

This is not an issue, I can create a patch just for boardinfo init fix.

> not the extra 'is slot
> free check'.

Even ignoring patch 1, it is necessary to check if the slot is free
because if SETDASA fails the boardinfo->init_dyn_addr can be assigned to
another device. That's why we need to check if expected_dyn_addr is free.

> Plus, I want the fix to be backported so we should avoid
> any unneeded deps.
>
> But even with those 2 things addressed, I'm still convinced the
> 'free desc when device is not reachable' change you do in patch 1 is
> not that great,

If I'm doing wrong I really appreciate you tell me the reason.

> and the fact that you can't pre-reserve the address to
> make sure no one uses it until the device had a chance to show up tends
> to prove me right.

This is a different corner case and I though we agreed that the framework
doesn't provide guarantees to assign boardinfo->init_dyn_addr [1].

Yet, I don't disagree with the idea of pre-reserve the
boardinfo->init_dyn_addr.
I can do this but we need to align how it should be done.

>
> Can we please do what I suggest and solve the "not enough dev slots"
> problem later on (if we really have to).

I have this use case where the HC has only 4 slot for 4 devices.
Sometimes the one or more devices can be sleeping and when they trigger
HJ there is no space in HC.

Best regards,
Vitor Soares

[1] https://patchwork.kernel.org/patch/11120841/

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