| Message ID | 9d02acd4-8a60-1ac3-00d9-8c99940254a2@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 21 Jun 2018 16:11:16 -0400 Stefan Berger <stefanb@linux.vnet.ibm.com> wrote: > On 06/21/2018 07:55 AM, Marc-André Lureau wrote: > > From: Stefan Berger <stefanb@linux.vnet.ibm.com> > > > > The TPM Physical Presence interface consists of an ACPI part, a shared > > memory part, and code in the firmware. Users can send messages to the > > firmware by writing a code into the shared memory through invoking the > > ACPI code. When a reboot happens, the firmware looks for the code and > > acts on it by sending sequences of commands to the TPM. > > > > This patch adds the ACPI code. It is similar to the one in EDK2 but doesn't > > assume that SMIs are necessary to use. It uses a similar datastructure for > > the shared memory as EDK2 does so that EDK2 and SeaBIOS could both make use > > of it. I extended the shared memory data structure with an array of 256 > > bytes, one for each code that could be implemented. The array contains > > flags describing the individual codes. This decouples the ACPI implementation > > from the firmware implementation. > > > > The underlying TCG specification is accessible from the following page. > > > > https://trustedcomputinggroup.org/tcg-physical-presence-interface-specification/ > > > > This patch implements version 1.30. > > > > Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com> > > > > --- > > > > v5 (Marc-André): > > - /struct tpm_ppi/struct TPMPPIData > > > > v4 (Marc-André): > > - replace 'DerefOf (FUNC [N])' with a function, to fix Windows ACPI > > handling. > > - replace 'return Package (..) {} ' with scoped variables, to fix > > Windows ACPI handling. > > > > v3: > > - add support for PPI to CRB > > - split up OperationRegion TPPI into two parts, one containing > > the registers (TPP1) and the other one the flags (TPP2); switched > > the order of the flags versus registers in the code > > - adapted ACPI code to small changes to the array of flags where > > previous flag 0 was removed and now shifting right wasn't always > > necessary anymore > > > > v2: > > - get rid of FAIL variable; function 5 was using it and always > > returns 0; the value is related to the ACPI function call not > > a possible failure of the TPM function call. > > - extend shared memory data structure with per-opcode entries > > holding flags and use those flags to determine what to return > > to caller > > - implement interface version 1.3 > > --- > > include/hw/acpi/tpm.h | 21 +++ > > hw/i386/acpi-build.c | 294 +++++++++++++++++++++++++++++++++++++++++- > > 2 files changed, 314 insertions(+), 1 deletion(-) > > > > diff --git a/include/hw/acpi/tpm.h b/include/hw/acpi/tpm.h > > index f79d68a77a..430605a8e5 100644 > > --- a/include/hw/acpi/tpm.h > > +++ b/include/hw/acpi/tpm.h > > @@ -196,4 +196,25 @@ REG32(CRB_DATA_BUFFER, 0x80) > > #define TPM_PPI_VERSION_NONE 0 > > #define TPM_PPI_VERSION_1_30 1 > > > > +struct TPMPPIData { > > + uint8_t func[256]; /* 0x000: per TPM function implementation flags; > > + set by BIOS */ > > +/* whether function is blocked by BIOS settings; bits 0, 1, 2 */ > > +#define TPM_PPI_FUNC_NOT_IMPLEMENTED (0 << 0) > > +#define TPM_PPI_FUNC_BIOS_ONLY (1 << 0) > > +#define TPM_PPI_FUNC_BLOCKED (2 << 0) > > +#define TPM_PPI_FUNC_ALLOWED_USR_REQ (3 << 0) > > +#define TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ (4 << 0) > > +#define TPM_PPI_FUNC_MASK (7 << 0) > > + uint8_t ppin; /* 0x100 : set by BIOS */ > > + uint32_t ppip; /* 0x101 : set by ACPI; not used */ > > + uint32_t pprp; /* 0x105 : response from TPM; set by BIOS */ > > + uint32_t pprq; /* 0x109 : opcode; set by ACPI */ > > + uint32_t pprm; /* 0x10d : parameter for opcode; set by ACPI */ > > + uint32_t lppr; /* 0x111 : last opcode; set by BIOS */ > > + uint32_t fret; /* 0x115 : set by ACPI; not used */ > > + uint8_t res1[0x40]; /* 0x119 : reserved for future use */ > > + uint8_t next_step; /* 0x159 : next step after reboot; set by BIOS */ > > +} QEMU_PACKED; > > + > > #endif /* HW_ACPI_TPM_H */ > > Here's a description of this interface. The SMM related fields, ppin, > ppip and fret could be > renamed to reserved fields since we are not supporting SMM. > > diff --git a/docs/specs/tpm.txt b/docs/specs/tpm.txt > index c230c4c93e..17d811f633 100644 > --- a/docs/specs/tpm.txt > +++ b/docs/specs/tpm.txt > @@ -42,6 +42,73 @@ URL: > > https://trustedcomputinggroup.org/tcg-acpi-specification/ > > +== ACPI PPI Interface == > + > +QEMU supports the Physical Presence Interface (PPI) for TPM 1.2 and TPM > 2. This > +interface requires ACPI and firmware support. The specification can be > found at > +the following URL: > + > +https://trustedcomputinggroup.org/resource/tcg-physical-presence-interface-specification/ > + > +PPI enables a system administrator (root) to request a modification to the > +TPM upon reboot. The PPI specification defines the operation requests > and the > +actions the firmware has to take. The system administrator passes the > operation > +request number to the firmware through an ACPI interface which writes this > +number to a memory location that the firmware knows. Upon reboot, the > firmware > +finds the number and sends commands to the the TPM. The firmware writes > the TPM > +result code and the operation request number to a memory location that > ACPI can > +read from and pass the result on to the administrator. > + > +The PPI specification defines a set of mandatory and optional > operations for > +the firmware to implement. The ACPI interface also allows an > administrator to > +list the supported operations. In QEMU the ACPI code is generated by > QEMU, yet > +the firmware needs to implement support on a per-operations basis, and > +different firmwares may support a different subset. Therefore, QEMU > introduces > +the virtual memory device for PPI where the firmware can indicate which > +operations it supports and ACPI can enable the ones that are supported and > +disable all others. This interface lies in main memory and has the > following > +layout: I'd prefer a table format to describe layout, like in docs/specs/acpi_nvdimm.txt or docs/specs/acpi_mem_hotplug.txt > + > + struct TPMPPIData { > + uint8_t func[256]; /* 0x000 */ > + /* whether function is blocked by BIOS settings; bits 0, 1, 2 */ > + #define TPM_PPI_FUNC_NOT_IMPLEMENTED (0 << 0) > + #define TPM_PPI_FUNC_BIOS_ONLY (1 << 0) > + #define TPM_PPI_FUNC_BLOCKED (2 << 0) > + #define TPM_PPI_FUNC_ALLOWED_USR_REQ (3 << 0) > + #define TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ (4 << 0) > + #define TPM_PPI_FUNC_MASK (7 << 0) > + uint8_t ppin; /* 0x100 */ > + uint32_t ppip; /* 0x101 */ > + uint32_t pprp; /* 0x105 */ > + uint32_t pprq; /* 0x109 */ > + uint32_t pprm; /* 0x10d */ > + uint32_t lppr; /* 0x111 */ > + uint32_t fret; /* 0x115 */ > + uint8_t res1[0x40]; /* 0x119 */ > + uint8_t next_step; /* 0x159 */ > + } QEMU_PACKED; > + > +For each code the firmware suppports, the firmware needs to set the > appropriate > +flags in the func array. The number of the operation serves as the > index for the > +array. > + > +The operation request's number is written into the pprq field. Any optional > +additional parameters needed by an operation request must be written into > +the pprm field. > + > +The firmware indicates the last executed command in the lppr field and > +writes the result into the pprp field. > + > +For SMM support, the field ppin describes the software SMI interrupt to > use. > +This field needs to be written by the firmware. The ppip field is used > +to pass the ACPI function number to the SMM code. This field needs to be > +written by ACPI. The fret field holds the result of the SMM operation and > +needs to be set by SMM code. > + > +Some operations require the firmware to reboot the machine before it can > +send more commands to the TPM. For this, the firmware can use the next_step > +field to remember what operation to execute after the reboot. > > QEMU files related to TPM ACPI tables: > - hw/i386/acpi-build.c > > > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > > index d9320845ed..4cb3ac9000 100644 > > --- a/hw/i386/acpi-build.c > > +++ b/hw/i386/acpi-build.c > > @@ -43,6 +43,7 @@ > > #include "hw/acpi/memory_hotplug.h" > > #include "sysemu/tpm.h" > > #include "hw/acpi/tpm.h" > > +#include "hw/tpm/tpm_ppi.h" > > #include "hw/acpi/vmgenid.h" > > #include "sysemu/tpm_backend.h" > > #include "hw/timer/mc146818rtc_regs.h" > > @@ -1789,6 +1790,292 @@ static Aml *build_q35_osc_method(void) > > return method; > > } > > > > +static void > > +build_tpm_ppi(Aml *dev) > > +{ > > + Aml *method, *name, *field, *ifctx, *ifctx2, *ifctx3, *pak; > > + struct TPMPPIData *tpm_ppi = NULL; > > + int i; > > + > > + /* > > + * TPP1 is for the flags that indicate which PPI operations > > + * are supported by the firmware. The firmware is expected to > > + * write these flags. > > + */ > > + aml_append(dev, > > + aml_operation_region("TPP1", AML_SYSTEM_MEMORY, > > + aml_int(TPM_PPI_ADDR_BASE), > > + sizeof(tpm_ppi->func))); > > + field = aml_field("TPP1", AML_ANY_ACC, AML_NOLOCK, AML_PRESERVE); > > + for (i = 0; i < sizeof(tpm_ppi->func); i++) { > > + char *tmp = g_strdup_printf("FN%02X", i); > > + aml_append(field, aml_named_field(tmp, BITS_PER_BYTE)); > > + g_free(tmp); > > + } > > + aml_append(dev, field); > > + > > + /* > > + * TPP2 is for the registers that ACPI code used to pass > > + * the PPI code and parameter (PPRQ, PPRM) to the firmware. > > + */ > > + aml_append(dev, > > + aml_operation_region("TPP2", AML_SYSTEM_MEMORY, > > + aml_int(TPM_PPI_ADDR_BASE + > > + offsetof(struct TPMPPIData, ppin)), > > + sizeof(struct TPMPPIData) - > > + sizeof(tpm_ppi->func))); > > + field = aml_field("TPP2", AML_ANY_ACC, AML_NOLOCK, AML_PRESERVE); > > + aml_append(field, aml_named_field("PPIN", > > + sizeof(uint8_t) * BITS_PER_BYTE)); > > + aml_append(field, aml_named_field("PPIP", > > + sizeof(uint32_t) * BITS_PER_BYTE)); > > + aml_append(field, aml_named_field("PPRP", > > + sizeof(uint32_t) * BITS_PER_BYTE)); > > + aml_append(field, aml_named_field("PPRQ", > > + sizeof(uint32_t) * BITS_PER_BYTE)); > > + aml_append(field, aml_named_field("PPRM", > > + sizeof(uint32_t) * BITS_PER_BYTE)); > > + aml_append(field, aml_named_field("LPPR", > > + sizeof(uint32_t) * BITS_PER_BYTE)); > > + aml_append(dev, field); > > + > > + method = aml_method("TPFN", 1, AML_SERIALIZED); > > + { > > + for (i = 0; i < sizeof(tpm_ppi->func); i++) { > > + ifctx = aml_if(aml_equal(aml_int(i), aml_arg(0))); > > + { > > + aml_append(ifctx, aml_return(aml_name("FN%02X", i))); > > + } > > + aml_append(method, ifctx); > > + } > > + aml_append(method, aml_return(aml_int(0))); > > + } > > + aml_append(dev, method); > > + > > + pak = aml_package(2); > > + aml_append(pak, aml_int(0)); > > + aml_append(pak, aml_int(0)); > > + name = aml_name_decl("TPM2", pak); > > + aml_append(dev, name); > > + > > + pak = aml_package(3); > > + aml_append(pak, aml_int(0)); > > + aml_append(pak, aml_int(0)); > > + aml_append(pak, aml_int(0)); > > + name = aml_name_decl("TPM3", pak); > > + aml_append(dev, name); > > + > > + method = aml_method("_DSM", 4, AML_SERIALIZED); > > + { > > + uint8_t zerobyte[1] = { 0 }; > > + > > + ifctx = aml_if( > > + aml_equal(aml_arg(0), > > + aml_touuid("3DDDFAA6-361B-4EB4-A424-8D10089D1653"))); > > + { > > + aml_append(ifctx, > > + aml_store(aml_to_integer(aml_arg(2)), aml_local(0))); > > + > > + /* standard DSM query function */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(0))); > > + { > > + uint8_t byte_list[2] = { 0xff, 0x01 }; > > + aml_append(ifctx2, aml_return(aml_buffer(2, byte_list))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* interface version: 1.3 */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(1))); > > + { > > + aml_append(ifctx2, aml_return(aml_string("1.3"))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* submit TPM operation */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(2))); > > + { > > + /* get opcode */ > > + aml_append(ifctx2, > > + aml_store(aml_derefof(aml_index(aml_arg(3), > > + aml_int(0))), > > + aml_local(0))); > > + /* get opcode flags */ > > + aml_append(ifctx2, > > + aml_store(aml_call1("TPFN", aml_local(0)), > > + aml_local(1))); > > + ifctx3 = aml_if( > > + aml_equal( > > + aml_and(aml_local(1), aml_int(TPM_PPI_FUNC_MASK), NULL), > > + aml_int(TPM_PPI_FUNC_NOT_IMPLEMENTED))); > > + { > > + /* 1: not implemented */ > > + aml_append(ifctx3, aml_return(aml_int(1))); > > + } > > + aml_append(ifctx2, ifctx3); > > + aml_append(ifctx2, aml_store(aml_local(0), aml_name("PPRQ"))); > > + aml_append(ifctx2, aml_store(aml_int(0), aml_name("PPRM"))); > > + /* 0: success */ > > + aml_append(ifctx2, aml_return(aml_int(0))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* get pending TPM operation */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(3))); > > + { > > + /* revision to integer */ > > + aml_append(ifctx2, > > + aml_store( > > + aml_to_integer(aml_arg(1)), > > + aml_local(1))); > > + ifctx3 = aml_if(aml_equal(aml_local(1), aml_int(1))); > > + { > > + aml_append(ifctx3, > > + aml_store( > > + aml_name("PPRQ"), > > + aml_index(aml_name("TPM2"), aml_int(1)))); > > + aml_append(ifctx3, aml_return(aml_name("TPM2"))); > > + } > > + aml_append(ifctx2, ifctx3); > > + > > + ifctx3 = aml_if(aml_equal(aml_local(1), aml_int(2))); > > + { > > + aml_append(ifctx3, > > + aml_store( > > + aml_name("PPRQ"), > > + aml_index(aml_name("TPM3"), aml_int(1)))); > > + aml_append(ifctx3, > > + aml_store( > > + aml_name("PPRM"), > > + aml_index(aml_name("TPM3"), aml_int(2)))); > > + aml_append(ifctx3, aml_return(aml_name("TPM3"))); > > + } > > + aml_append(ifctx2, ifctx3); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* get platform-specific action to transition to pre-OS env. */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(4))); > > + { > > + /* reboot */ > > + aml_append(ifctx2, aml_return(aml_int(2))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* get TPM operation response */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(5))); > > + { > > + aml_append(ifctx2, > > + aml_store( > > + aml_name("LPPR"), > > + aml_index(aml_name("TPM3"), aml_int(1)))); > > + aml_append(ifctx2, > > + aml_store( > > + aml_name("PPRP"), > > + aml_index(aml_name("TPM3"), aml_int(2)))); > > + aml_append(ifctx2, aml_return(aml_name("TPM3"))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* submit preferred user language */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(6))); > > + { > > + /* 3 = not implemented */ > > + aml_append(ifctx2, aml_return(aml_int(3))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* submit TPM operation v2 */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(7))); > > + { > > + /* get opcode */ > > + aml_append(ifctx2, > > + aml_store(aml_derefof(aml_index(aml_arg(3), > > + aml_int(0))), > > + aml_local(0))); > > + /* get opcode flags */ > > + aml_append(ifctx2, > > + aml_store(aml_call1("TPFN", aml_local(0)), > > + aml_local(1))); > > + ifctx3 = aml_if( > > + aml_equal( > > + aml_and(aml_local(1), aml_int(TPM_PPI_FUNC_MASK), NULL), > > + aml_int(TPM_PPI_FUNC_NOT_IMPLEMENTED))); > > + { > > + /* 1: not implemented */ > > + aml_append(ifctx3, aml_return(aml_int(1))); > > + } > > + aml_append(ifctx2, ifctx3); > > + > > + ifctx3 = aml_if( > > + aml_equal( > > + aml_and(aml_local(1), aml_int(TPM_PPI_FUNC_MASK), NULL), > > + aml_int(TPM_PPI_FUNC_BLOCKED))); > > + { > > + /* 3: blocked by firmware */ > > + aml_append(ifctx3, aml_return(aml_int(3))); > > + } > > + aml_append(ifctx2, ifctx3); > > + > > + /* revision to integer */ > > + aml_append(ifctx2, > > + aml_store( > > + aml_to_integer(aml_arg(1)), > > + aml_local(1))); > > + > > + ifctx3 = aml_if(aml_equal(aml_local(1), aml_int(1))); > > + { > > + /* revision 1 */ > > + aml_append(ifctx3, aml_store(aml_local(0), > > + aml_name("PPRQ"))); > > + aml_append(ifctx3, aml_store(aml_int(0), > > + aml_name("PPRM"))); > > + } > > + aml_append(ifctx2, ifctx3); > > + > > + ifctx3 = aml_if(aml_equal(aml_local(1), aml_int(2))); > > + { > > + /* revision 2 */ > > + aml_append(ifctx3, > > + aml_store(aml_local(0), aml_name("PPRQ"))); > > + aml_append(ifctx3, > > + aml_store( > > + aml_derefof(aml_index(aml_arg(3), > > + aml_int(1))), > > + aml_name("PPRM"))); > > + } > > + aml_append(ifctx2, ifctx3); > > + /* 0: success */ > > + aml_append(ifctx2, aml_return(aml_int(0))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + /* get user confirmation status for operation */ > > + ifctx2 = aml_if(aml_equal(aml_local(0), aml_int(8))); > > + { > > + /* get opcode */ > > + aml_append(ifctx2, > > + aml_store(aml_derefof(aml_index(aml_arg(3), > > + aml_int(0))), > > + aml_local(0))); > > + /* get opcode flags */ > > + aml_append(ifctx2, > > + aml_store(aml_call1("TPFN", aml_local(0)), > > + aml_local(1))); > > + /* return confirmation status code */ > > + aml_append(ifctx2, > > + aml_return( > > + aml_and(aml_local(1), > > + aml_int(TPM_PPI_FUNC_MASK), NULL))); > > + } > > + aml_append(ifctx, ifctx2); > > + > > + aml_append(ifctx, aml_return(aml_buffer(1, zerobyte))); > > + } > > + aml_append(method, ifctx); > > + } > > + aml_append(dev, method); > > +} > > + > > static void > > build_dsdt(GArray *table_data, BIOSLinker *linker, > > AcpiPmInfo *pm, AcpiMiscInfo *misc, > > @@ -2153,6 +2440,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > > */ > > /* aml_append(crs, aml_irq_no_flags(TPM_TIS_IRQ)); */ > > aml_append(dev, aml_name_decl("_CRS", crs)); > > + > > + build_tpm_ppi(dev); > > + > > aml_append(scope, dev); > > } > > > > @@ -2172,6 +2462,8 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > > aml_append(method, aml_return(aml_int(0x0f))); > > aml_append(dev, method); > > > > + build_tpm_ppi(dev); > > + > > aml_append(sb_scope, dev); > > } > > > > @@ -2920,7 +3212,7 @@ void acpi_setup(void) > > tpm_config = (FWCfgTPMConfig) { > > .tpmppi_address = cpu_to_le32(TPM_PPI_ADDR_BASE), > > .tpm_version = cpu_to_le32(tpm_get_version(tpm_find())), > > - .tpmppi_version = cpu_to_le32(TPM_PPI_VERSION_NONE) > > + .tpmppi_version = cpu_to_le32(TPM_PPI_VERSION_1_30) > > }; > > fw_cfg_add_file(pcms->fw_cfg, "etc/tpm/config", > > &tpm_config, sizeof tpm_config); > > >
diff --git a/docs/specs/tpm.txt b/docs/specs/tpm.txt index c230c4c93e..17d811f633 100644 --- a/docs/specs/tpm.txt +++ b/docs/specs/tpm.txt @@ -42,6 +42,73 @@ URL: https://trustedcomputinggroup.org/tcg-acpi-specification/ +== ACPI PPI Interface == + +QEMU supports the Physical Presence Interface (PPI) for TPM 1.2 and TPM 2. This +interface requires ACPI and firmware support. The specification can be found at +the following URL: + +https://trustedcomputinggroup.org/resource/tcg-physical-presence-interface-specification/ + +PPI enables a system administrator (root) to request a modification to the +TPM upon reboot. The PPI specification defines the operation requests and the +actions the firmware has to take. The system administrator passes the operation +request number to the firmware through an ACPI interface which writes this +number to a memory location that the firmware knows. Upon reboot, the firmware +finds the number and sends commands to the the TPM. The firmware writes the TPM +result code and the operation request number to a memory location that ACPI can +read from and pass the result on to the administrator. + +The PPI specification defines a set of mandatory and optional operations for +the firmware to implement. The ACPI interface also allows an administrator to +list the supported operations. In QEMU the ACPI code is generated by QEMU, yet +the firmware needs to implement support on a per-operations basis, and +different firmwares may support a different subset. Therefore, QEMU introduces +the virtual memory device for PPI where the firmware can indicate which +operations it supports and ACPI can enable the ones that are supported and +disable all others. This interface lies in main memory and has the following +layout: + + struct TPMPPIData { + uint8_t func[256]; /* 0x000 */ + /* whether function is blocked by BIOS settings; bits 0, 1, 2 */ + #define TPM_PPI_FUNC_NOT_IMPLEMENTED (0 << 0) + #define TPM_PPI_FUNC_BIOS_ONLY (1 << 0) + #define TPM_PPI_FUNC_BLOCKED (2 << 0) + #define TPM_PPI_FUNC_ALLOWED_USR_REQ (3 << 0) + #define TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ (4 << 0) + #define TPM_PPI_FUNC_MASK (7 << 0) + uint8_t ppin; /* 0x100 */ + uint32_t ppip; /* 0x101 */ + uint32_t pprp; /* 0x105 */ + uint32_t pprq; /* 0x109 */ + uint32_t pprm; /* 0x10d */ + uint32_t lppr; /* 0x111 */ + uint32_t fret; /* 0x115 */ + uint8_t res1[0x40]; /* 0x119 */ + uint8_t next_step; /* 0x159 */ + } QEMU_PACKED; + +For each code the firmware suppports, the firmware needs to set the appropriate +flags in the func array. The number of the operation serves as the index for the +array. + +The operation request's number is written into the pprq field. Any optional +additional parameters needed by an operation request must be written into +the pprm field. + +The firmware indicates the last executed command in the lppr field and