Re: [PATCH v4 04/23] cxl: Add common helpers for cdat parsing

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 19 Apr 2023 13:21:25 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> Add helper functions to parse the CDAT table and provide a callback to
> parse the sub-table. Helpers are provided for DSMAS and DSLBIS sub-table
> parsing. The code is patterned after the ACPI table parsing helpers.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
A few minor things inline.   More than possible you addressed them
in earlier versions though.

Jonathan

> ---
> v2:
> - Use local headers to handle LE instead of ACPI header
> - Reduce complexity of parser function. (Jonathan)
> - Directly access header type. (Jonathan)
> - Simplify header ptr math. (Jonathan)
> - Move parsed counter to the correct location. (Jonathan)
> - Add LE to host conversion for entry length
> ---
>  drivers/cxl/core/Makefile |    1 
>  drivers/cxl/core/cdat.c   |  100 +++++++++++++++++++++++++++++++++++++++++++++
>  drivers/cxl/cxlpci.h      |   29 +++++++++++++
>  3 files changed, 130 insertions(+)
>  create mode 100644 drivers/cxl/core/cdat.c
> 
> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index ca4ae31d8f57..867a8014b462 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -12,5 +12,6 @@ cxl_core-y += memdev.o
>  cxl_core-y += mbox.o
>  cxl_core-y += pci.o
>  cxl_core-y += hdm.o
> +cxl_core-y += cdat.o
>  cxl_core-$(CONFIG_TRACING) += trace.o
>  cxl_core-$(CONFIG_CXL_REGION) += region.o
> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
> new file mode 100644
> index 000000000000..210f4499bddb
> --- /dev/null
> +++ b/drivers/cxl/core/cdat.c
> @@ -0,0 +1,100 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright(c) 2023 Intel Corporation. All rights reserved. */
> +#include "cxlpci.h"
> +#include "cxl.h"
> +
> +static bool has_handler(struct cdat_subtable_proc *proc)

Even though they are static, I'd add a cxl_ or cdat_ prefix
to these to make it clear they are local.

> +{
> +	return proc->handler;
> +}
> +
> +static int call_handler(struct cdat_subtable_proc *proc,
> +			struct cdat_subtable_entry *ent)
> +{
> +	if (has_handler(proc))

Do we need to check this again? It's checked in the parse_entries code
well before this point.

Also, if moving to checking it once, then is it worth the
little wrapper functions?


> +		return proc->handler(ent->hdr, proc->arg);
> +	return -EINVAL;
> +}
> +
> +static bool cdat_is_subtable_match(struct cdat_subtable_entry *ent)
> +{
> +	return ent->hdr->type == ent->type;
> +}
> +
> +static int cdat_table_parse_entries(enum cdat_type type,
> +				    struct cdat_header *table_header,
> +				    struct cdat_subtable_proc *proc)
> +{
> +	unsigned long table_end, entry_len;
> +	struct cdat_subtable_entry entry;
> +	int count = 0;
> +	int rc;
> +
> +	if (!has_handler(proc))
> +		return -EINVAL;
> +
> +	table_end = (unsigned long)table_header + table_header->length;
> +
> +	if (type >= CDAT_TYPE_RESERVED)
> +		return -EINVAL;
> +
> +	entry.type = type;
> +	entry.hdr = (struct cdat_entry_header *)(table_header + 1);
> +
> +	while ((unsigned long)entry.hdr < table_end) {
> +		entry_len = le16_to_cpu(entry.hdr->length);
> +
> +		if ((unsigned long)entry.hdr + entry_len > table_end)
> +			return -EINVAL;
> +
> +		if (entry_len == 0)
> +			return -EINVAL;
> +
> +		if (cdat_is_subtable_match(&entry)) {
> +			rc = call_handler(proc, &entry);
> +			if (rc)
> +				return rc;
> +			count++;
> +		}
> +
> +		entry.hdr = (struct cdat_entry_header *)((unsigned long)entry.hdr + entry_len);
> +	}
> +
> +	return count;
> +}

...

> +int cdat_table_parse_sslbis(struct cdat_header *table,
> +			    cdat_tbl_entry_handler handler, void *arg)

Feels like these ones should take a typed arg.  Sure you'll loose
that again to use the generic handling code, but at this level we can 
do it I think.

> +{
> +	struct cdat_subtable_proc proc = {
> +		.handler	= handler,
> +		.arg		= arg,
> +	};
> +
> +	return cdat_table_parse_entries(CDAT_TYPE_SSLBIS, table, &proc);
> +}