[PATCH v4 5/6] ata: libata: Add libata.force parameter max_sec

[Niklas Cassel <cassel@kernel.org>]

Add a new libata.force parameter called max_sec.

The parameter can take an arbitrary value using the format:
libata.force=max_sec=<number of 512B sectors>

e.g. libata.force=max_sec=8191
or
libata.force=max_sec=2048

This will allow the user to set an arbitrary maximum command size
(dev->max_sectors) using libata.force.

We cannot remove the existing libata.force parameters "max_sec_128" and
"max_sec_1024", as these are a part of the exising user facing API.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +++++
 drivers/ata/libata-core.c                       | 1 +
 2 files changed, 6 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6c42061ca20e5..e47113cbd2fcc 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3294,6 +3294,11 @@
 			* [no]logdir: Enable or disable access to the general
 			  purpose log directory.
 
+			* max_sec=<sectors>: Set the transfer size limit, in
+			  number of 512-byte sectors, to the value specified in
+			  <sectors>. The value specified in <sectors> has to be
+			  a non-zero positive integer.
+
 			* max_sec_128: Set transfer size limit to 128 sectors.
 
 			* max_sec_1024: Set or clear transfer size limit to
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 9a8da530e123a..2905aceba7038 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6536,6 +6536,7 @@ static const struct ata_force_param force_tbl[] __initconst = {
 
 	force_quirk_val(max_sec_128,	ATA_QUIRK_MAX_SEC,	128),
 	force_quirk_val(max_sec_1024,	ATA_QUIRK_MAX_SEC,	1024),
+	force_quirk_on(max_sec=,	ATA_QUIRK_MAX_SEC),
 	force_quirk_on(max_sec_lba48,	ATA_QUIRK_MAX_SEC_LBA48),
 
 	force_quirk_onoff(lpm,		ATA_QUIRK_NOLPM),
-- 
2.52.0