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usb_block_drv: allow for using UAS devices via BOT

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USB Attached SCSI devices might expose a bulk-only interface
as fall-back at interface 0 and alternate setting 0. This commit
allows for probing all alternate settings of the active interface
to be able to use such devices.

The configuration was extended so that in case the device interface
is known beforehand the driver can be configured accordingly.

Fixes #4494.
This commit is contained in:
Josef Söntgen 2022-04-27 16:25:44 +00:00 committed by Christian Helmuth
parent 27444617e1
commit 87021d9fb1
2 changed files with 52 additions and 4 deletions
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12
repos/os/src/drivers/usb_block/README
View File

@ -8,13 +8,16 @@ Behavior
This driver only supports USB Mass Storage Bulk-Only devices that use the
SCSI Block Commands set (direct-access). Devices using different command
sets, e.g, SD/HC devices or some external disc drives will not work properly
if at all. The following configuration snippets demonstrates how to use the
driver:
if at all. The driver will query the device and tries to use the first
bulk-only interface it finds.
The following configuration snippets demonstrates how to use the driver:
!<start name="usb_block_drv">
! <resource name="RAM" quantum="4M"/>
! <provides> <service name="Block"/> </provides>
! <config label="usb_stick" report="yes" writeable="yes" interface="0" lun="0" reset_device="no" verbose_scsi="no"/>
! <config label="usb_stick" report="yes" writeable="yes" interface="0"
! alt_setting="0" lun="0" reset_device="no" verbose_scsi="no"/>
! <route>
! <service name="Usb"> <child name="usb_drv"/> </service>
! <any-service> <parent/> <any-child/> </any-service>
@ -61,7 +64,8 @@ In addition to other attributes that can be used to configure sepecific aspects
of the driver. The 'writeable' attribute denotes the permission of the Block
session client to write to the USB device. Independent thereof the driver will
query the device and will set the Block session operations accordingly. The
'interface' specifies the USB interface the driver should use. If the device
'interface' specifies the USB interface the driver should use and 'alt_setting'
allows for selecting the appropriate alternate setting. If the device
provides multiple SCSI devices the 'lun' attribute is used to select the right
one. When 'reset_device' is enabled, a 'bulk-only mass storage reset' command
is sent to the device at the beginning of the initialization step. This command

44
repos/os/src/drivers/usb_block/main.cc
View File

@ -170,6 +170,9 @@ struct Usb::Block_driver : Usb::Completion
uint8_t active_interface = 0;
uint8_t active_lun = 0;
enum { INVALID_ALT_SETTING = 256 };
uint16_t active_alt_setting = 0;
uint32_t active_tag = 0;
uint32_t new_tag() { return ++active_tag % 0xffffffu; }
@ -431,6 +434,43 @@ struct Usb::Block_driver : Usb::Completion
IPROTO_BULK_ONLY = 80
};
/*
* Devices following the USB Attached SCSI specification
* normally expose the bulk-only transport in interface 0 alt 0
* and the UAS endpoints in interface 0 alt 1.
*
* The default interface and thereby 'iface.current()', however,
* might point to the interface 0 alt 1 for such devices.
*
* In case the alternate setting was not explicitly configured
* we look for the first bulk-only setting.
*/
if (active_alt_setting == INVALID_ALT_SETTING) {
/* cap value in case there is no bulk-only */
active_alt_setting = 0;
for (unsigned i = 0; i < iface.alternate_count(); i++) {
Alternate_interface &aif = iface.alternate_interface(i);
if (aif.iclass == ICLASS_MASS_STORAGE
&& aif.isubclass == ISUBCLASS_SCSI
&& aif.iprotocol == IPROTO_BULK_ONLY) {
active_alt_setting = i;
Genode::log("Use probed alternate setting ",
active_alt_setting, " for interface ",
active_interface);
break;
}
}
}
Alternate_interface &aif =
iface.alternate_interface((uint8_t)active_alt_setting);
iface.set_alternate_interface(aif);
Alternate_interface &alt_iface = iface.current();
if (alt_iface.iclass != ICLASS_MASS_STORAGE
@ -782,6 +822,10 @@ struct Usb::Block_driver : Usb::Completion
active_lun = node.attribute_value("lun", 0UL);
reset_device = node.attribute_value("reset_device", false);
verbose_scsi = node.attribute_value("verbose_scsi", false);
active_alt_setting =
node.attribute_value("alt_setting",
(unsigned long)INVALID_ALT_SETTING);
}
/**