On Fri, 2023-11-03 at 15:05 +0000, Jonathan Cameron wrote:
> On Fri, 3 Nov 2023 16:45:20 +1030
> Andrew Jeffery <and...@codeconstruct.com.au> wrote:
>
> > I ran out of spoons before I could come up with a better client tracking
> > scheme back in the original refactoring series:
> >
> > https://lore.kernel.org/all/20210608104757.582199-1-and...@aj.id.au/
> >
> > Jonathan prodded Konstantin about the issue in a review of Konstantin's
> > MCTP patches[1], prompting an attempt to clean it up.
> >
> > [1]: https://lore.kernel.org/all/20230929120835.00001...@huawei.com/
> >
> > Prevent client modules from having to track their own instances by
> > requiring they return a pointer to a client object from their
> > add_device() implementation. We can then track this in the core, and
> > provide it as the argument to the remove_device() implementation to save
> > the client module from further work. The usual container_of() pattern
> > gets the client module access to its private data.
> >
> > Signed-off-by: Andrew Jeffery <and...@codeconstruct.com.au>
>
> Hi Andrew,
>
> A few comments inline.
> More generally, whilst this is definitely an improvement I'd have been tempted
> to make more use of the linux device model for this with the clients added
> as devices with a parent of the kcs_bmc_device. That would then allow for
> simple dependency tracking, binding of individual drivers and all that.
>
> What you have here feels fine though and is a much less invasive change.
Yeah, I had this debate with myself before posting the patches. My
reasoning for the current approach is that the clients don't typically
represent a device, rather a protocol implementation that is
communicated over a KCS device (maybe more like pairing a line
discipline with a UART). It was unclear to me whether associating a
`struct device` with a protocol implementation was stretching the
abstraction a bit, or whether I haven't considered some other
perspective hard enough - maybe we treat the client as the remote
device, similar to e.g. a `struct i2c_client`?
>
> Jonathan
>
>
> > diff --git a/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
> > b/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
> > index 98f231f24c26..9fca31f8c7c2 100644
> > --- a/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
> > +++ b/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
> > @@ -71,8 +71,6 @@ enum kcs_ipmi_errors {
>
>
>
> > +static struct kcs_bmc_client *
> > +kcs_bmc_ipmi_add_device(struct kcs_bmc_driver *drv, struct kcs_bmc_device
> > *dev)
> > {
> > struct kcs_bmc_ipmi *priv;
> > int rc;
> >
> > priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> > if (!priv)
> > - return -ENOMEM;
> > + return ERR_PTR(ENOMEM);
> As below. I thought it took negatives..
I should have double checked that. It requires negatives. Thanks.
> >
> > spin_lock_init(&priv->lock);
> > mutex_init(&priv->mutex);
> > init_waitqueue_head(&priv->queue);
> >
> > - priv->client.dev = kcs_bmc;
> > - priv->client.ops = &kcs_bmc_ipmi_client_ops;
> > + kcs_bmc_client_init(&priv->client, &kcs_bmc_ipmi_client_ops, drv, dev);
> >
> > priv->miscdev.minor = MISC_DYNAMIC_MINOR;
> > - priv->miscdev.name = kasprintf(GFP_KERNEL, "%s%u", DEVICE_NAME,
> > kcs_bmc->channel);
> > + priv->miscdev.name = kasprintf(GFP_KERNEL, "%s%u", DEVICE_NAME,
> > dev->channel);
> > if (!priv->miscdev.name) {
> > rc = -ENOMEM;
> ERR_PTR
I converted it to an ERR_PTR in the return after the cleanup_priv
label. Maybe it's preferable I do the conversion immediately? Easy
enough to change if you think so.
> > goto cleanup_priv;
>
>
>
> ...
>
> > diff --git a/drivers/char/ipmi/kcs_bmc_serio.c
> > b/drivers/char/ipmi/kcs_bmc_serio.c
> > index 0a68c76da955..3cfda39506f6 100644
> > --- a/drivers/char/ipmi/kcs_bmc_serio.c
> > +++ b/drivers/char/ipmi/kcs_bmc_serio.c
>
> ...
>
>
> > +static struct kcs_bmc_client *
> > +kcs_bmc_serio_add_device(struct kcs_bmc_driver *drv, struct kcs_bmc_device
> > *dev)
> > {
> > struct kcs_bmc_serio *priv;
> > struct serio *port;
> > @@ -75,12 +71,12 @@ static int kcs_bmc_serio_add_device(struct
> > kcs_bmc_device *kcs_bmc)
> >
> > priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> > if (!priv)
> > - return -ENOMEM;
> > + return ERR_PTR(ENOMEM);
> >
> > /* Use kzalloc() as the allocation is cleaned up with kfree() via
> > serio_unregister_port() */
> > port = kzalloc(sizeof(*port), GFP_KERNEL);
> > if (!port) {
> > - rc = -ENOMEM;
> > + rc = ENOMEM;
> Why positive?
> Doesn't ERR_PTR() typically get passed negatives?
Ack, as above.
Thanks for the review,
Andrew
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